Solar Panels

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Solar Panels A solar panel (also solar module, photovoltaic module or photovoltaic panel) is a packaged, connected assembly of photovoltaic cells. The solar panel can be used as a component of a larger photovoltaic system to generate and supply electricity in commercial and residential applications. Each panel is rated by its DC output power under standard test conditions, and typically ranges from 100 to 320 watts. The efficiency of a panel determines the area of a panel given the same rated output - an 8% efficient 230 watt panel will have twice the area of a 16% efficient 230 watt panel. Because a single solar panel can produce only a limited amount of power, most installations contain multiple panels. A photovoltaic system typically includes an array of solar panels, an inverter, and sometimes a battery and or solar tracker and interconnection wiring.
 Theory and Construction

Solar panels use light energy (photons) from the sun to generate electricity through the photovoltaic effect. The majority of modules use wafer-based crystalline silicon cells or thin-film cells based on cadmium telluride or silicon. The structural (load carrying) member of a module can either be the top layer or the back layer. Cells must also be protected from mechanical damage and moisture. Most solar panels are rigid, but semi-flexible ones are available, based on thin-film cells. These early solar panels were first used in space in 1958. Electrical connections are made in series to achieve a desired output voltage and/or in parallel to provide a desired current capability. The conducting wires that take the current off the panels may contain silver, copper or other non-magnetic conductive transition metals. The cells must be connected electrically to one another and to the rest of the system. Externally, popular terrestrial usage photovoltaic panels use MC3 (older) or MC4 connectors to facilitate easy weatherproof connections to the rest of the system. Bypass diodes may be incorporated or used externally, in case of partial panel shading, to maximize the output of panel sections still illuminated. The p-n junctions of mono-crystalline silicon cells may have adequate reverse voltage characteristics to prevent damaging panel section reverse current. Reverse currents could lead to overheating of shaded cells. Solar cells become less efficient at higher temperatures and installers try to provide good ventilation behind solar panels. Some recent solar panel designs include concentrators in which light is focused by lenses or mirrors onto an array of smaller cells. This enables the use of cells with a high cost per unit area (such as gallium arsenide) in a cost-effective way.
 Storing energy in a solar panel

The potential energy available via solar power might seem limitless on a sunny summer day, but all that energy has to be stored for it to be truly useful. If you see a solar panel on a rooftop, in a large-scale array, or even on a parking meter, a bulky battery or

supercapacitor is hidden just out of sight, receiving energy from the panel through power lines.  However, that's a storage method that doesn't scale well for solar-powered devices with no space for a battery pack.  In a quest for a smaller, more self-sustaining solar power source, a UW-Madison electrical engineer has proposed a design for solar panels that can simultaneously generate power from sunlight and store power reserves for later, all within a single device.  Hongrui Jiang and his students developed the idea, published in the journal Advanced Materials June 6. Jiang is the Vilas Distinguished Achievement Professor of electrical and computer engineering at UW-Madison and specializes in microscale devices. He and his students developed the technology as an offshoot of a National Institutes of Health grant to design a self-focusing contact lens that adapts to the eyes of adults suffering from presbyopia, a natural aging process that stiffens the lens and reduces the eye's ability to focus, especially at short distances.  To power that contact lens, Jiang and his team have worked out a design that balances energy harvesting, storage and usage. "We needed a multi-functional and small-formfactor device in order to integrate it all into a single contact lens structure," says Jiang.  The top layer of each photovoltaic cell is a conventional photo electrode, converting sunlight into electrons. During that conversion process, the electrons split off into two directions: most electrons flow out of the device to support a power load, while some are directed to a polyvinylidene fluoride polymer (PVDF) coated on zinc oxide nanowires. The PVDF has the high dielectric constant required to serve as an energy storage solution. "When there's no sunlight, the stored power will come back through the nano wires to power the load."  The final design allows for a standard-size solar cell that can simultaneously power a device and store energy for later use, creating a closed-loop system for small-scale applications of solar energy. "We can have some energy set aside locally, right in the panel, so that when you need it, you can get it," says Jiang.

The final design allows for a standard-size solar cell that can simultaneously power a device and store energy for later use.

Other such solar panels — referred to as photovoltaic self-charging cells — have been around for a while, but the ability to provide energy continuously, rain or shine, sets Jiang's apart.

Currently, Jiang's proof of concept converts only 4 percent of the sunshine striking the photoreceptor into usable electricity — and that's approximately 20 percent less efficient than most commercial solar panels in use today. However, as Jiang and his team refine the design from a standard-size photovoltaic cell to their specific use, they expect both the conversion efficiency and the amount of energy they can store to improve.

Since the design scales up easily, says Jiang, microgrids — small scale power grids used to balance renewable power sources in energy-efficient buildings — would be another ideal application, since self-contained solar panels would limit the need for battery management and would allow engineers to design buildings that rely on the outside power grid even less than current systems.

And there are futuristic applications: picture lighting systems that can be installed in remote areas — without running expensive power lines. "You could have one solar panel installed that will store the energy the system might need through nights and cloudy days," says Jiang. -

 Solar energy Resources

Solar radiation, often called the solar resource, is a general term for the electromagnetic radiation emitted by the sun. Solar radiation can be captured and turned into useful forms of energy, such as heat and electricity, using a variety of technologies. However, the technical feasibility and economical operation of these technologies at a specific location depends on the available solar resource. Basic Principles

Every location on Earth receives sunlight at least part of the year. The amount of solar radiation that reaches any one spot on the Earth's surface varies according to:
    

Geographic location Time of day Season Local landscape Local weather.

Because the Earth is round, the sun strikes the surface at different angles, ranging from 0° (just above the horizon) to 90° (directly overhead). When the sun's rays are vertical, the Earth's surface gets all the energy possible. The more slanted the sun's rays are, the longer they travel through the atmosphere, becoming more scattered and diffuse. Because the Earth is round, the frigid polar regions never get a high sun, and because of the tilted axis of rotation, these areas receive no sun at all during part of the year. The Earth revolves around the sun in an elliptical orbit and is closer to the sun during part of the year. When the sun is nearer the Earth, the Earth's surface receives a little more solar energy. The Earth is nearer the sun when it is summer in the southern hemisphere and winter in the northern hemisphere. However, the presence of vast oceans moderates the hotter summers and colder winters one would expect to see in the southern hemisphere as a result of this difference. The 23.5° tilt in the Earth's axis of rotation is a more significant factor in determining the amount of sunlight striking the Earth at a particular location. Tilting results in longer days in the northern hemisphere from the spring (vernal) equinox to the fall (autumnal) equinox and longer days in the southern hemisphere during the other 6 months. Days and nights are both exactly 12 hours long on the equinoxes, which occur each year on or around March 23 and September 22. Countries such as the United States, which lie in the middle latitudes, receive more solar energy in the summer not only because days are longer, but also because the sun is nearly overhead. The sun's rays are far more slanted during the shorter days of the winter months. Cities such as Denver, Colorado, (near 40° latitude) receive nearly three times more solar energy in June than they do in December. The rotation of the Earth is also responsible for hourly variations in sunlight. In the early morning and late afternoon, the sun is low in the sky. Its rays travel further through the atmosphere than at noon, when the sun is at its highest point. On a clear day, the greatest amount of solar energy reaches a solar collector around solar noon. Diffuse and Direct Solar Radiation As sunlight passes through the atmosphere, some of it is absorbed, scattered, and reflected by:
 

Air molecules Water vapor

    

Clouds Dust Pollutants Forest fires Volcanoes.

This is called diffuse solar radiation. The solar radiation that reaches the Earth's surface without being diffused is called direct beam solar radiation. The sum of the diffuse and direct solar radiation is called global solar radiation. Atmospheric conditions can reduce direct beam radiation by 10% on clear, dry days and by 100% during thick, cloudy days. Measurement Scientists measure the amount of sunlight falling on specific locations at different times of the year. They then estimate the amount of sunlight falling on regions at the same latitude with similar climates. Measurements of solar energy are typically expressed as total radiation on a horizontal surface,or as total radiation on a surface tracking the sun. Radiation data for solar electric (photovoltaic) systems are often represented as kilowatt-hours per square meter (kWh/m2). Direct estimates of solar energy may also be expressed as watts per square meter (W/m2). Radiation data for solar water heating and space heating systems are usually represented in British thermal units per square foot (Btu/ft2).

 How is solar energy stored in solar panels?
Answer: Trick question - it's not! Solar panels do not store energy but convert the Sun's energy into electricity. This direct current (DC) electricity (energy) is then transferred immediately through wires to a load (something that uses energy). For most residential uses, solar energy must be inverted from DC to AC (alternating current) which is the type of energy most houses use. So, actually, solar energy is not stored in solar panels, but converted into useable energy by solar panels.

 Dear EarthTalk: How does the microwave compare in energy use, say, to using a gas or electric
stove burner to heat water for a cup of tea?

-- Tempie, Dexter, MI

The short answer is that it depends upon several variables, including the price of electricity versus gas, and the relative efficiency of the appliances involved. Typically, though, a microwave would be slightly more efficient at heating water than the flame on a gas stove, and should use up a little less energy. The reason: The microwave’s heat waves are focused on the liquid (or food) inside, not on heating the air or container around it, meaning that most if not all of the energy generated is used to make your water ready. Given this logic, it is hard to believe that a burner element on an electric stovetop would be any better, but an analysis by Home Energy Magazine found otherwise. The magazine’s researchers discovered that an electric burner uses about 25 percent less electricity than a microwave in boiling a cup of water. That said, the difference in energy saved by using one method over another is negligible: Choosing the most efficient process might save a heavy tea drinker a dollar or so a year. ―You’d save more energy over the year by replacing one light bulb with a CFL [compact fluorescent lightbulb] or turning off the air conditioner for an hour—not an hour a day, one hour at some point over the whole year,‖ says consumer advocate Michael Bluejay. Although a microwave may not save much energy or money over a stove burner when heating water, it can be much more energy-efficient than a traditional full-size oven when it comes to cooking food. For starters, because their heat waves are concentrated on the food, microwaves cook and heat much faster than traditional ovens. According to the federal government’s Energy Star program, which rates appliances based on their energy-efficiency, cooking or re-heating small portions of food in the microwave can save as much as 80 percent of the energy used to cook or warm them up in the oven. The website reports that there are other things you can do to optimize your energy efficiency around the kitchen when cooking. For starters, make sure to keep the inside surfaces of your microwave oven clean so as to maximize the amount of energy reflected toward your food. On a gas stovetop, make sure the flame is fully below the cookware; likewise, on an electric stovetop, make sure the pan or kettle completely covers the heating element to minimize wasted heat. Also, use the appropriate size pan for the job at hand, as smaller pans are cheaper and more energy-efficient to heat up.

Despite these tips for cooking greener, Bluejay reiterates that most of us will hardly put a dent in our overall energy use just by choosing one appliance over another. According to his analysis, for someone who bakes three hours a week the cheapest cooking method saves only an estimated $2.06/month compared to the most expensive method. ―Focusing on cooking methods is not the way to save electricity [at home],‖ says Bluejay. ―You should look at heating, cooling, lighting and laundry instead.‖

 Readers Respond: Gas or Electric Stoves? Which do you prefer and why.

I have had an electric stove over thirty years that was wonderful! My husband and I purchased a gas stove and all I have had is trouble. The top is very hard to clean. It takes longer than fifteen minutes to heat. I have burned my hands on pots. It appears longer to boil water, etc. More important is that I noticed the foods were taking longer to heat, wouldn't cook properly, even to a pot pie I made. We had three service calls. The oven gage read exactly with the service mans gauge. I bought a gas thermometer and tried again. The thermometer only read t hat our oven was heating to 350% and I was correct! Service came again tested and said the oven was fine and read up to 450%. Can the brand new gauge be wrong? Now the store has agreed to take the stove back and I can choose whatever I want. I am totally confused as I read more plus signs to gas than electric and fell did we have a lemon gas stove. Any suggestions? thanks! Bless you all! —Guest Dorothy B. Jo Electric all the way....flat cooktop is so much easier to clean..I have never had any problems cooking or baking....and I am afraid of gas....I am sure that it also depends on the product purchased.....I love KitchenAid appliances. —Guest Jo Gas I hate electric it sucks takes forever to cook gas cooked foid taste alot better —Guest Unknown pushkin I am about to make a serious investment in a stove and don't know which decision to make. I like to 'specialise in making fine pastries as well as ordinary stuff, but which will give a better product...gas or electricity? I live in Eastern Europe where the price of gas is almost of no consequence and elctricity is

dearer. I have always insisted that I want an electric oven but..... Can anyone advise me PLEASE? Thank you.Jackie —Guest jackie

BEFORE IT'S TOO LATE! It's as simple as this. If your top priority is the end result of the food you cook (the quality and all), then choose GAS (much better control over the temperature). BUT if your MORE CONCERN with your HEALTH (and the health of others) and specially the ENVIRONMENT, then you know what to choose! You don't need to be a chef or a environmentalist to figure this out. LOL! —Guest -Mother NatureDual Fuel I have a Dual Fuel range. Gas burners and electric oven. The best of both worlds. —Guest Benjamin Gas all the way.. Right now I am in an electric house. No gas whatsoever. Nothing gets cooked to the correct temperature —Guest The rooster Electric ofcourse.. An inductive surface elimminates the problem with afterheating and also uses less power than conventional electric stoves. Also i get nervous in houses that has gas in them as i fear leakage for some reason. In Sweden there is only a few really old houses at all in the entire country that has gas pipelines to them (less then a hundred buildings in total) so there is not much of a choise anyways. And gas is damn expensive. —Guest Egon Ruuda It really depends. Gas stoves are great for cooking, but installation can be very difficult. Creating or modifying gas pipes can be an expensive operation. Most of the new houses and apartments has already the electric installation, so electric stoves/ovens can be easier to install and ready to use. On the other hand, electric stoves tend to be more expensive in the long run and cooking may be slower than gas, but for a person that is not expert in cooking this may be a good thing. If you are planning for business, then things are different. Gas is what you must have. —Guest Sophie Glass top

Have had both types. Yes, gas has more control, but the hours I raked up cleaning the gas stove and those awful electrical rings are now lost. Dump the gas top, stick with gas oven. Don't get caught up in the hype of red knobs. —Guest p

Gas, gas, gas! I've always had gas, with the exception of one apartment years ago, which had an electric stove. Seems everything either burnt or cooked unevenly, it took forever to heat up and and made cooking, which I usually enjoy, a largely unpleasent experience. Since then, it's been nothing but gas, and any apartment or condo I consider in the future, MUST have a gas stove; electric is an automatic dealbreaker. —Guest Mar Gas cooker I much prefer cooking with gas my previous oven was electric never enjoyed using it, results are better with gas. —Guest Rima domestic engineer I would love an electric flat surface cooktop with a gas oven. If they exist, where can I get one? —Guest K.M. Kruczek Piggyx2 I prefer gas cook tops and electric ovens. With gas cook tops I can control the temp. needed quickly. In the oven I need a constant temp. and electric seems to do better than gas there. —Guest Lynda Estabrook RETIRED NAVY COOK [SUBMARINES] I preffer gas stoves as it is a lot easier to get the temps. right and cooking is faster.I have cooked almost 30 yrs. and i've used both. —Guest thomas andrews

 Components: The Solar Panel is Only the Beginning

A properly installed and maintained system not only saves you money and gives you energy independence, but is environmentally friendly, too. Solar power panels, or modules, are what

most people think of when they think of a solar power "system," although they are in fact just one cog in the system. This guide is a short introduction each component in the system and to help give you a full picture to how the system works to provide clean cheap energy for your home. The individual solar cells The "photovoltaic effect" is a straightforward process by which solar cells convert sunlight into usable electricity. The earliest solar cells converted only 1-2% of the sun's light energy into usable electric energy, whereas today's units can convert some 15-20% of sunlight's energy. Increasing panel efficiency allows for smaller, cheaper systems, which in turn allows for greater accessibility for varying income brackets as well as physical applications. The solar power modules (solar panels and other types) A solar power module, often called a "solar panel", is essentially an array of many individual solar cells; a module will produce from 50 to 220 watts. All of the major manufacturers—Kyocera, PowerLight, Sharp, SunPower and others—build modules with 25-30-year useful lives. Generally speaking, solar modules of all efficiency ratings from any of the established manufacturers are reliable and offer good return on investment. Solar inverters A key component in your solar system device chain is the inverter. Inverters modify the solar energy modules' current and voltage to maximize output, and convert their DC power to the AC power required by most of business and home equipment. Inverters are rated and compared to one another based on their capacity, their voltage rating and their battery capabilities. Often they are installed along with fuse boxes, switches and other electrical components in a "control center" that relies on certified electrical service boxes. Inverters should typically be mounted in dust-free, dry and well-ventilated areas. Racks, mounts and roof attachments for solar systems To withstand years of exposure (wind, weather, corrosion, etc.) the solar array has to be solidly mounted. It may appear from street level that solar panels are directly atop a house's roof, but this is not the case. Mounting on roofs has to take into account the roofing materials, their condition, their future replacement needs and so on. A professional solar installer knows the ins and outs of all mounting alternatives, and you are strongly advised not to jeopardize your home's roof by going up yourself to nail down some panels. Wiring and meters For long-term stability and efficient operation, there is probably no more important component than the one you probably will see least, the wiring. You will have to follow construction codes

as well as the National Electrical Code, and use devices that carry a rating agency certification, as from Underwriters Laboratory (Check with your installer that he/she is up to date with these requirements). Connections can become loose over time from ongoing "rooftop heat cycling," and this is a common cause of poor system performance, it's always a good idea to have a plan in place should your system ever experience an issue. Monitoring Systems To monitor system performance, it may be useful to install a separate solar power electric meter. Finally, you may also consider a separate "AC disconnect" so you can isolate your solar power from the utility's power. Your solar power system will likely include a DC disconnect, as well, to isolate your array output from your inverter. If there is a power outage at your utility, your solar system will continue producing power and could actually feed power into the grid while utility crews work to resolve the power outage. Bottom line A solar system is a chain of devices that takes power from once source (the sun) and makes it usable in your home. You can think of it as even a kind of organism, taking in fuel and converting it to practical use by way of light bulbs, radios, toasters and other appliances. All of the pieces of you solar power system need to work together, and when they do you are able to reduce your energy costs, help the environment and make a serious contribution to a realistic, sustainable future.

 Solar Energy Systems - Tapping The Sun's Energy

In this illustration of solar energy systems, you can see exactly how the sun's energy is converted into electricity that is usable by your home or business. Follow the path of energy from the sun, through the pv panels, its conversion to AC electricity by the inverter and finally into the utility grid. Take a look for a detailed explanation of solar energy.

 Top 10 Solar Energy Myths 1. Solar panels do not work in cold, cloudy places/states. UV light is all that's needed and even the cloudiest of places have excelled. Germany, who ranks low in sunny days, is the solar energy capital of the world. In fact, when the solar panels are cold, they are able to better conduct electricity. 2. Solar systems are too expensive. Solar Energy Installations are more affordable than they have ever been. In every state, incentives cover a minimum of 30% all the way up to 85% of the system costs. The cost per watt, installed, is at an all time low of $8. 3. Solar panels require constant maintenance. The panels rarely require maintenance or cleaning, plus the average warranty lasts 25 years! 4. Solar systems are ugly, large and bulky. Solar panels have come a long way over the years. Now systems have become virtually seamless with solar shingles. Solar cells can be combined with slate, metal, fiber-cement, and asphalt roofing. 5. Few states offer rebates or financial incentives for solar energy installations. According to the Database of State Incentives for Renewable Energy, 48 states have a solar/renewable energy incentive on top of the 30% federal tax credit! 6. The solar panels cannot withstand harsh climates (snow, hail, winds, sleet). The University of Vermont (who receives considerable snow fall) has a system that has proven to be effective and virtually maintenance free, even during the winter months. The color of the solar panels is dark which aides in melting the snow plus a South facing position allows for a quickened process. 7. Solar systems are unreliable and inconsistent. On the contrary, solar electric systems can be more reliable than the utility company. They have no moving parts and off-grid systems are not subject to power outages. In fact, solar technologies are used to power many vital systems: aircraft warning lights, railroad crossing signals, navigational buoys, etc. 8. I cannot use solar energy because I don't have Southern roof exposure. East/West roof exposure is also effective for photovoltaic systems. Another option is a ground mounted system in which case all you need is a relatively flat, unshaded area. 9. Solar energy is inefficient. According to the U.S. Department of Energy, solar panel efficiency has more than quadrupled since the 1970's. With an average between 15-19% it sits in the same efficiency range as the gas in your car. Unlike gas though, the technology continues to advance, in turn, so will efficiency. 10. I won't live in the home long enough to make my investment back. Actually, a solar system increases the value of the home. For every $1,000 that has been saved in annual

electric costs, your home's value rises $20,000. (U.S. Department of Housing and Urban Development).

 13 Fundamental Advantages and Disadvantages of Solar Energy By Greg Whitburn

Solar energy is becoming increasingly popular as the world begins to take notice of the burgeoning carbon emission problems that come with burning fossil fuels. But why all the fuss? Nay-sayers have become less and less vocal as solar energy’s popularity has grown increasingly unhindered. Below I will discuss the advantages and disadvantages of solar energy. Advantages of Solar Energy  No green house gases

Advantages and disadvantages of solar energy: The major benefit of solar is avoiding green house gases that fossil fuels produce. The first and foremost advantage of solar energy is that it does not emit any green house gases. Solar energy is produced by conducting the sun’s radiation – a process void of any smoke, gas, or other chemical by-product. This is the main driving force behind all green energy technology, as nations attempt to meet climate change obligations in curbing emissions.

Italy’s Montalto di Castro solar park is a good example of solar’s contribution to curbing emissions. It avoids 20,000 tonnes per year of carbon emissions compared to fossil fuel energy production.  Infinite Free Energy

Another advantage of using solar energy is that beyond initial installation and maintenance, solar energy is one hundred percent free. Solar doesn’t require expensive and ongoing raw materials like oil or coal, and requires significantly lower operational labor than conventional power production. Lower costs are direct as well as indirect – less staff working at the power plant as the sun and the solar semi conductors do all the work, as well as no raw materials that have to be extracted, refined, and transported to the power plant.  Decentralization of power

Solar energy offers decentralization in most (sunny) locations, meaning self-reliant societies. Oil, coal, and gas used to produce conventional electricity is often transported cross-country or internationally. This transportation has a myriad of additional costs, including monetary costs, pollution costs of transport, and roading wear and tear costs, all of which is avoided with solar. Of course, decentralization has its limits as some locations get more sunlight than others.  Going off the grid with solar

Solar Barn: Going off grid is a huge advantage of solar power for people in isolated locations. Solar energy can be produced on or off the grid.

On grid means a house remains connected to the state electricity grid. Off grid has no connection to the electricity grid, so the house, business or whatever being powered is relying solely on the solar or solar-hybrid. The ability to produce electricity off the grid is a major advantage of solar energy for people who live in isolated and rural areas. Power prices and the cost of installing power lines are often exorbitantly high in these places and many have frequent power-cuts. Many city-dwellers are also choosing to go off the grid with their alternate energy as part of a self-reliant lifestyle.  Solar jobs

A particularly relevant and advantageous feature of solar energy production is that it creates jobs. The EIAA states that Europe’s solar industry has created 100,000 jobs so far. Solar jobs come in many forms, from manufacturing, installing, monitoring and maintaining solar panels, to research and design, development, cultural integration, and policy jobs. The book Natural Capitalism has a very appropriate view of the employment benefits of green design and a prudent approach to using resources. The book proposes that while green technology and increased employment cost alot of money, much greater money can be saved through simple but drastically improved resource efficiency. With solar energy currently contributing only an estimated 4% of the world’s electricity, and an economic-model where raw materials don’t have to be indefinitely purchased and transported, it’s reasonable so assume solar jobs are sustainable if the solar industry can survive the recession.  Solar’s avoidance of politics and price volatility

One of the biggest advantages of solar energy is the ability to avoid the politics and price volatility that is increasingly characterizing fossil fuel markets. The sun is an unlimited commodity that can be adequately sourced from many locations, meaning solar avoids the price manipulations and politics that have more than doubled the price of many fossil fuels in the past decade. While the price of fossil fuels have increased, the per watt price of solar energy production has more than halved in the past decade – and is set to become even cheaper in the near future as better technology and economies of scale take effect. Furthermore, the ever-abundant nature of the sun’s energy would hint at a democratic and competitive energy market – where wars aren’t fought over oil fields and high-demand raw materials aren’t controlled by monopolies.

Of course, a new form of politics has emerged with regard to government incentives and the adoption of solar, however these politics are arguably incomparable to the fossil fuel status quo.  Saving eco-systems and livelihoods

Because solar doesn’t rely on constantly mining raw materials, it doesn’t result in the destruction of forests and eco-systems that occurs with most fossil fuel operations. Destruction can come in many forms, from destruction through accepted extraction methods, to more irresponsible practices in vulnerable areas, to accidents. Major examples include Canada’s tar sands mining which involves the systematic destruction of the Boreal Forest (which accounts for 25% of the world’s intact forest land), and creates toxic by-product ponds large enough to see from space [1]. The Niger Delta is an example where excessive and irresponsible oil extraction practices have poisoned fishing deltas previously used by villagers as the main source of food and employment, creating extremely desperate poverty and essentially decimating villages [2]. A more widely known, but arguably lower human-cost incident is the 2010 BP oil spill in the Gulf of Mexico. It killed 11 people and spilled 780 thousand cubic meters of crude oil into the sea.

An interesting glance at the situation caused by destructive fossil fuel company practices in the Niger Delta. Sweet Crudeis a good documentary if you want to learn more.

The best is yet to come

Solar technology is currently improving in leaps and bounds. Across the world, and particularly in Europe, savvy clean technology researchers are making enormous developments in solar technology. What was expensive, bulky, and inefficient yesterday, is becoming cheaper, more accessible, and vastly more efficient each week. Disadvantages of Solar Energy  Solar doesn’t work at night

Obviously the biggest disadvantages of solar energy production revolve around the fact that it’s not constant. To produce solar electricity there must be sunlight. So energy must be stored or sourced elsewhere at night. Beyond daily fluctuations, solar production decreases over winter months when there are less sunlight hours and sun radiation is less intense.

Solar Inefficiency

A very common criticism is that solar energy production is relatively inefficient. Currently, widespread solar panel efficiency – how much of the sun’s energy a solar panel can convert into electrical energy – is at around 22%. This means that a fairly vast amount of surface area is required to produce a lot of electricity. However, efficiency has developed dramatically over the last five years, and solar panel efficiency should continue to rise steadily over the next five years. For the moment though, low efficiency is a relevant disadvantage of solar. Solar inefficiency is an interesting argument, as efficiency is relative. One could ask ―inefficient compared to what?‖ And ―What determines efficiency?‖ Solar panels currently only have a radiation efficiency of up to 22%, however they don’t create the carbon by-product that coal produces and doesn’t require constant extraction, refinement, and transportation – all of which surely carry weight on efficiency scales.  Storing Solar

Solar electricity storage technology has not reached its potential yet. While there are many solar drip feed batteries available, these are currently costly and bulky, and more appropriate to small scale home solar panels than large solar farms.  Solar panels are bulky

Solar panels are bulky. This is particularly true of the higher-efficiency, traditional silicon crystalline wafer solar modules. These are the large solar panels that are covered in glass. New technology thin-film solar modules are much less bulky, and have recently been developed as applications such as solar roof tiles and ―amorphous‖ flexible solar modules. The downfall is that thin-film is currently less efficient than crystalline wafer solar.  One of the biggest disadvantages of solar energy – COST

The main hindrance to solar energy going widespread is the cost of installing solar panels. Capital costs for installing a home solar system or building a solar farm are high. Particularly obstructive is the fact that installing solar panels has large upfront costs – after which the energy trickles in for free. Imagine having to pay upfront today for your next 30 years worth of power.

That’s an incredibly disadvantageous feature of solar energy production, particularly during a time of recession. Currently a mega watt hour of solar energy costs well over double a mega watt hour of conventional electricity (exact costs vary dramatically depending on location). All is not lost though – nuclear is a good example (economically) of energy production that was initially incredibly expensive, but became more feasible when appropriate energy subsidies were put in place.

Solar Energy Gets People Talking

One of the accompanying advantages and disadvantages of solar energy and other green tech is that they’re making us re-assess how things are valued in society, and how things like economics, environment, and investment are handled. There is debate and polarization of perspectives and interests. While not everybody is in favor of solar (some more aggressively than others), the fact that there is discussion about the validity of the status quo – the monopolistic nature of many industries, the problems with solely focusing on economics, and environmental disregard – is a fascinating development, a development that some may term an ideological revolution. At a practical level, many governments and state authorities are encouraging solar use through incentives such as subsidies, rebates and tariffs. California is a good example of how such measures can work. Spain highlights the importance of long-term consideration with such incentives, and how they can fail if not handled correctly or if circumstances change, such as the global financial crisis. Factors such as cheaper materials and installation as demand grows will make solar more affordable in the future, but for the moment, the fact is that producing solar electricity is financially expensive compared to conventional methods.

 Benefits of Using Solar Panels to Charge Small Devices

Apart from major appliances that you need to wash clothes, preserve food, and heat water, you may want to stay connected to the internet and keep your phones/tablet PC charged during power outages.

This article is primarily about long power outages caused by hurricanes that last days or even weeks (Hurricane Ivan left me without power for two weeks). If you don’t want to spend much and just want to keep your phones charged, then you could do so at a lower cost by using a small solar setup (depending on how many devices you want to charge) instead of a typical gasoline-powered generator that would cost hundreds of dollars. This is due to the fact that generators are normally larger than necessary (often over 1,000 watts), and therefore more expensive than necessary. Before you buy a factory-prebuilt solar charger or set one up yourself, you should know the power consumption of the devices you need to sustain.

To sustain your wi-fi internet connection, you probably need at least 10 watts of power. As an example, the DSL modem that I have uses 6 watts, and the wi-fi router uses 4 watts. Cell phones use a fraction of a watt, and tablet PCs use less than 3 watts. Cellphone chargers, however, draw about 5 watts (example: Blackberry 8320) if they are smartphones — generally, for less than an hour. The power consumption averages out to less than 1 watt. Parts list (to sustain 1 smartphone and wi-fi internet connection only):
  

Inverter — all the inverters I have seen are over 100 watts, and those cost very little (less than $30). 12 volt, 7 Ah deep-cycle lead-acid battery — this size has much better than average value ($20). 20 watt solar panel with a charge controller if your area enjoys more than 10 hours of sunny weather daily ($70). Total cost: $120. Other notes: The inverter will beep when the battery is low. Start conserving stringently as soon as it starts occasional beeping. Fast beeping means that your time is up. Turn off the modem and router first so you can save the battery for the phone. Cost of phone-only USB solar charger: less than $30.

 Solar Fueled Stoves

Solar powered stoves harness UV radiation from the sun and convert it to heat. The possible applications and limitation seem obvious, but many are surprised that even simple systems may boil and/or pasteurize water. In sunny areas, you have the ability for long term cooking or snow melting without the need for fuel resupply. This is an incredible feature for those in remote areas where local fuel is limited or cost prohibitive. Of course solar cooker performance is limited by weather, latitude, and seasonal variations but may be enhanced by altitude where there is greater UV radiation. There is a lot of published designs incorporating various box, panel and dish plans. But with the bulk, weight and inherent limitations of most designs, few are practical for most hiker's general use One useful application for solar cookers might be for base camp snow melting where you can let the sun do its job while you're out and about. Advantages include:  potential for unlimited pollution free cooking  no fuel needed so no extra weight of bulk for longer trips  clean  airline checkable  cheap to make and free to operate  pasteurize water (65° C or 150° F x 20 minutes) without fuel  won't burn food Disadvantages include:  weight, bulk  weather dependent  backpack versions tend to be very slow to cook (hour plus)  can't cook at night  must cook in the open away from shade (near mountains, under trees, in depressions, by large hikers, etc.)  improper use or accidents can result in serious eye damage or fire - always use eye UV protection

Most solar cookers incorporate a few common concepts  reflect/concentrate sunlight from a wide area and focus it on your pot/oven o mirrors o polished metal o foil o Mylar o inside surface of potato chip bags o metallic auto sunshade o aluminumized or Mylar bubble wrap o Mylar balloons o space blankets o etc  convert solar energy to heat by using black pots/ovens to absorb light o black aluminum pots o black painted canning jars (these allow pressurized air to escape) o thinner rather than thicker walled pots o tight fitting lids are ideal  transparent insulators trap heat while allowing light to pass through causing a greenhouse-like effect o flat glass o plastic bake bags o plastic bottles o glass jars, inverted bowls, etc o disposable high-density polyethylene plastic bags There are three common cooker types: 1. Panel Cookers - aka Combination Cookers Use foldable reflective panels that generally concentrate heat. These do not focus light as precisely as parabolic cookers, so do not reach as high a temperatures, but also do not need to be adjusted as much to work. These are light and simple to construct. 2. Parabolic Cookers - aka Curved Concentrator Cookers 3. Box Cookers


11.5oz SOLTAC CookSack. SOLTAC's CookSack is one of the very few commercial solar cookers marketed for backpacking. It consists of a plastic bag with a transparent top and a Mylar bottom to reflect sunlight, a black pot, pot stand, and accessories to tie down your cook system. To operate, open the bag up, trap some air, set up pot on pot stand in bag, tie everything down and wait. Some weight can be trimmed off the CookSack system by replacing the 6.2oz pot with something lighter, possibly making a lighter than 2oz 6 9/16" pot stand, and by using Spectra cord for tie downs. A homemade version may be constructed out of large bake bags and foil or potato chip bags.

14oz Backpack Cooker The Backpack Cooker is another commercial solar cooker that's a little more solid than the CookSack with a pretty simple design that can be easily replicated with the right materials.

9oz Foil on Folded Cardboard Pot is 12oz drink can with lid in a bake bag set on the bottom of a plastic 2liter bottle

10"x10"x2" Folded Various packable solar cookers for hiking can be made from a mix of cardboard, metallic auto sunshades, Mylar or aluminum bubble wrap, Mylar sheets, foil, chip bags, aluminum flashing, space blankets, plastic bottles, plastic bake bags and other materials.

Ziploc Bag Snow Melter Placing snow in a plastic bag or bottle allows you to catch and trap heat from the sun to melt snow.

Winter Solar Water Collector You can use a space blanket, tarp, trash bag or foam pad to melt and collect water from snow. Insulating the collector with a foam pad will increase this solar collector's effectiveness. Don't be surprised if your water tastes a little plastic if you use a garbage bag or other plastic sheeting to melt snow. wintcamp

 How to Store Solar Energy By Pier55

If you’ve ever wondered how to store solar energy here are the basics. Solar energy is energy from the sun which is collected here on earth for heating, lighting and other human needs. Many of our basic energy needs can be addressed by using solar power. This can be done directly or indirectly but is not easy to do on a large scale. To store solar energy two components are required. A means of collecting the solar energy and a way to generate it are needed to make sure we can access the sun’s energy. The collector collects the sun’s radiation and converts some of it to another form of energy such as electricity and heat. It is critical to find a way to store solar energy. This is because the sun does not shine for 24 hours a day and on overcast days the energy is inhibited. The storage equipment is a way to accumulate excess energy when the sun’s rays are at maximum strength. When the sun is not shining or obscured this stored energy can be used. A backup supply also forms part of this system for times when the stored energy is insufficient. There are many ways to store solar energy. Three types of collectors are used to collect the sun’s radiation: 1) flat-plate collectors, 2) focusing collectors and 3) passive collectors. Solar energy is very well suited for heating purposes. This heat energy can be stored in a liquid like water or a packed bed. A packed bed is a container in which small objects like stones can be placed. The stones are able to store solar energy. Heat energy can also be stored in phasechanger or heat-of-fusion units which use chemicals to alter solid to liquid at certain temperatures. Later the liquid can return to its solid form and the energy can be used. This process is often used to store solar energy in homes to heat water. The water itself acts as the means to store solar energy. A tank is filled with hot water during the day and used when it’s required. Swimming pools can also be heated using solar energy. The water in the pool may act as a storage medium or a packed bed may be used instead. Solar energy can be used to heat homes. In this case a lot more energy is needed. This means that larger solar panels need to be used to store solar energy. Heat-of-fusion storage units are usually used for this purpose but packed bed or hot water tanks are also sometimes used. It can be quite expensive to purchase large panels and a storage system to heat a large building. If a building is heated by solar power passive collectors are used with other storage systems.

One type of passive energy collector is the incidental heat trap. In this system heat enters through a window and falls on a stone floor. During the day the floor absorbs the heat and stays cool. At night the heat is released and heating is achieved. Another way to store solar energy is thermo-siphoning walls or roofs. In this system the heat that is absorbed and wasted in the walls and roof can be channeled for heating the home.

 How to Store Solar Energy With Car Batteries

By Peter Johnson, eHow Contributor

Solar photovoltaic panel The electricity produced by a solar photovoltaic (PV) panel can be stored in any kind of battery that stores electricity. Car batteries can easily do this job. However, a small device called a charge controller or charge regulator is needed to ensure that the batteries are not overcharged by the solar panel when the panel is generating electricity and the batteries are fully charged. Things You'll Need      Solar panel Charge controller Tape measure Battery interconnect cables Electric cables


Preparation 1. Check the information regarding your solar panels and make sure they are designed to power a 12-volt system. Some solar panels can be wired up for 24 volts. In this case, the panels would generate a voltage that would seriously damage a 12-volt battery. 2. Place the batteries inside your building in a well-ventilated space. The 12-volt batteries must be connected in parallel. This means that the positive terminals of the car batteries will be connected together. Then, the negative terminals will be connected together. Count how many battery interconnect cables you need to hook up the batteries in parallel. 3. Trace the path of the cables linking the batteries and the solar panels and measure this distance as accurately as you can. Multiply this distance by two. This is the length of cable you will need. The gauge or thickness of the cable is important. The higher the current produced by the solar panels, the thicker the cable should be. Consult one of the many websites that show you how to chose the correct AWG number for the cables that run between the solar panels and the batteries. 4. Use a charge controller to control the charging current from the solar panels to the batteries. Charge controllers are sized for the maximum current generated by the solar panels in full sunshine. Go to a store that sells solar energy equipment and supplies, or check out one of the many websites on the Internet. Buy the charge controller, the battery interconnects, and the length of cable required. Installation 1. Install the charge controller on a wall close to the batteries. Connect the battery interconnects so that the batteries are connected in parallel. 2. Connect the solar panels and the batteries to the charge controller. A charge controller will have three sets of terminal connections each marked plus and minus: two terminals for the batteries, two terminals for the panels and two for the load. The manual that comes with the charge controller will show you how to connect up the batteries and the panels. 3. Check to make sure your solar PV system now delivers 12 volts direct current (DC) from the batteries. There are many small appliances that run on 12-volts DC, but more often the charge controller is connected to an inverter that will produce 110 volts alternating current (AC) from the 12-volt DC batteries. The AC current from the inverter can then be used to power any typical household appliance-- always assuming that the inverter can handle the load.

 How can we effectively store solar energy?

Matthew Panzer, an assistant professor of chemical engineering, lays out the options May 13, 2013

Meeting the world’s ever-growing energy demands in an environmentally responsible and sustainable manner is one of the most pressing issues facing us. Solar energy—sunlight—is an abundant, clean, safe and free resource, providing approximately 1,000 watts of power per square meter to Earth’s surface on a sunny day. In fact, the total amount of solar energy that hits Earth in just two hours is more than enough to meet current global energy consumption for an entire year. How can we most effectively capture, convert and store this tremendous natural resource? First, it is important to recognize that sunlight consists of a spectrum of wavelengths. About half of it is lower energy infrared radiation that we cannot see, but we feel as heat. The rest is higher energy visible light or ultraviolet light. Some technologies for harnessing solar energy target the entire spectrum, while others use only a portion of the available wavelengths. One of the first technologies that comes to mind when discussing solar energy is the growing use of solar cells, also known as photovoltaics, which convert sunlight directly into electricity. Solar cells are silent, non-polluting and long-lived devices that typically convert 10 to 15 percent of the energy received into energy that can be used. They are not the only way to get electricity from solar energy, though. Sunlight can also be intensely focused onto a small area, using an array of mirrors or lenses to heat water and create steam. High-pressure steam can be driven through a turbine to generate electricity. When the sun shines, we can store the electricity generated by solar cells or steam-driven turbines by using batteries (technically energy stored as electrochemical potential) or supercapacitors (energy stored in an electric field, due to the spatial separation of positive and negative charges). Then we can release electrical energy when it is cloudy or at night. There are at least two other ways to store solar energy for use later. First, the thermal energy of concentrated sunlight can be stored in the heat capacity of a molten salt (the liquid form of an ionic compound like sodium chloride) at a high temperature. When electricity is needed later, heat is transferred from the molten salt to water, using a heat exchanger to generate steam to drive a turbine. A second method of harnessing and storing solar energy is to employ sunlight to produce a fuel. For example, a photoelectrochemical cell uses solar energy to split water into hydrogen and oxygen gases, which can be stored as fuels. These gases are then recombined to generate electricity in a device known as a fuel cell. An attractive feature of this approach is that the byproduct of the fuel cell reaction is simply water. We should not forget that sunlight can also be used to directly heat a tank of water located outside the home, and that solar heated water can be used for washing or showering; this is common in parts of the developing world. While many of the technologies described here are in use on a small scale today, we must continue to develop innovative methods of storing solar energy and promote sustainable energy policies that benefit generations to come.


 What are the advantages and disadvantages between gas, liquid and solid fuel?

It seems you can get fuel for stoves in either gas form (butane, propane, etc.) liquid (methylated spirit) or solid fuel tablets. What are the particular advantages and disadvantages with each format, and when might you use one over the other?
Petroleum, Gas, White Gas, other liquid petrol products Stove weight: 12+ oz (340+ g) Water Boil per 100g fuel (rough): 5 to 6L Good:
   

Works below freezing incredibly good heat fuel is easy to come by fuel energy density is high enough so that just the fuel in the tank is enough for a few days, so no need to bring extra fuel cans.

   

Heavy high maintenance must pack out fuel cans more likely to go boom

Alcohol (liquid) Stove weight: 0.25 for a DIY Stove (7.1g) Good:
 

Minimal equipment needed good for ultralight setups

   

almost impossible to make it go boom very easy to light/use In a pinch you can use a wide variety of fuels making resupply a non-issue Ridiculously cheap gear. My entire kit cost $5 and I got a beer out of it.


Poor effective heat/weight of the fuel (due to burn rate, but still good for ultralight due to minimal gear need) Won't work as well in extreme cold. It requires extra gear, like a preheater, as shown in this Trangia video. Here's some extra testing from another hiker here. Alcohol is hard to light in deep cold and it's extremely hard/nigh impossible to boil water with it in sub freezing temps. Pretty finicky to use, at least with a DIY setup. In bright light it is sometimes easy to miss the flame and not realize it is still lit, creating a possible hazard.

 

Butane, Propane, Isobutane (pressurized gas) Stove weight: 3 to 5oz (85 to 142g) Water Boil per 100g fuel (rough): 7 to 8L Good:
  

good heat lightweight stove options available Wind, what wind? I've successfully boiled water in near freezing temps and high winds just by huddling over my MSR to dampen the wind (which is a pretty poor wind screen).

   

Must carry multiple canisters for long trips canisters can discharge while packed if not packed carefully must pack out fuel cans use of a heat shield requires very special care to avoid canister explosion (however a heat shield is a nice to have instead of a must have in most conditions with this setup)

Note: Sometimes it will work below freezing, sometimes it won't. It's a function of how it's handled. Also has issues at altitude. That's because these work by the liquid inside boiling and releasing gas out the top of the canister which doesn't work as well at lower pressure or temperature. Some designs address this by inverting the canister.

Hexamine (solid fuel) Stove weight: <1 oz (<28g) Good:
  

Super lightweight easy to get at stops and small towns boils water well

   

Not very good for other cooking (due to smell) soots pots with this sticky goo contaminates everything if not handled very carefully. hard to start and will not heat well in wind without an excellent wind screen


Gas vs. Electric Cooking calculator
Cost of fuel Gas: $

/ therm

Electricity: $
1 day/w k


/ kWh

Oven use ? Stove burners

30 minutes


30 minutes


5 days/w k


30 minutes


5 days/w k

(not used)

30 minutes


5 days/w k

(not used)

30 minutes


5 days/w k

Cost per year
(oven + burners)

Gas Range

Electric Range

 Energy used by cooking

Pilot light model Electric ignitor model

$57 $19

w/Standard oven w/Convection oven

$45 $43

Natural Electric: cheaper?

Gas Which

vs. is
Electric oven (standard)

Induction stovetop $32 w/Convection oven $6.24

Natural gas is almost
Electric oven (convection) $4.336799999999999



Gas oven (elec. ignitor) Gas oven (pilot) Slow cooker Toaster oven Microwave oven $4.342 $3.6400000000000005 $2 $1 $1

electricity. Of course, if you don't cook very

much, the savings won't be that great. Electric

stoves account for only 2.8% of electric use for households that have

them. (The oven part of the stoves comprises only 1.8%.) (DOE, 2001) The calculator at right will help you find which is cheaper for your own particular situation, according to how much you cook and your local fuel rates. Note that if you don't already have gas lines in your home then you'd have to pay to have them installed, which could easily cost hundreds of dollars. And when you sign up for gas service, you'll pay ~$12/mo. for the privilege of being a customer of the gas company, no matter how little gas you actually use. You'll need to weigh these costs against the savings the calculator shows for switching from electric to gas. Regardless of which is cheaper, gas presents two special problems, which is why I don't use gas in my own home even though it's cheaper: 1. Gas means a risk of explosion. Having a gas line in your home means that it's much more likely to accidentally explode. True, most people's kitchens don't blow up, but some of them certainly do.

2. Gas means air pollution. The combustion of gas produces poisons in indoor air. The problem with air pollution from gas ovens/stoves is so bad that I found this in a Whirlpool oven manual from 2003: "The health of some birds is extremely sensitive to the fumes given off [by the oven]. Exposure to the fumes may result in death to certain birds. Always move birds to another closed and well ventilated room." While the problem is more serious for birds it exists for people, too. A study commissioned by the Air Resources Board of California showed that gas ovens generate unhealthy levels of combustion byproducts like carbon monoxide and nitrogen dioxide. (It also showed that the self-cleaning mode generated a lot of indoor air pollution, whether it was a gas or an electric oven.) If you do use gas, the Children's Health Environmental Coalition has a list of ways to reduce gas pollution in your home. Make sure to put your own local fuel rates into the calculator! Everyone's local cost for gas and electricity is different. You'll need to look up your actual rate on your bills, otherwise the calculator results will be unreliable.

Remember also that rates will change in the future. The cost of natural gas doubled from 2005 to 2008, and then it dropped by 50% from 2008 to 2012. What's true today might not be true tomorrow. Here's more on natural gas prices. Also note that if you're trying to save energy for environmental reasons (rather than saving money), then what you eat is more important than how you cook it. For example, meat requires tremendous amounts of energy to produce, so substituting more vegetables, beans, and grains lowers your energy footprint dramatically. It takes 68 times more fossil fuel to produce beef than potatoes, for example. (source) Trying to figure out the most energy-efficient way to cook meat is like trying to figure out the optimal speed to drive a huge SUV for the best fuel economy. Meatless meals require far less overall energy, every time. (more...)

Tips to save on energy and costs when cooking

Use a solar oven. This is the main way of cooking in Mr. Electricity's household. It's remarkably easy to use and gets plenty hot — 300-350°F. And somehow foods don't seem to burn. We can put something in the oven and then even if we forget about it for hours, it's just fine later. The unit pictured is the $260 Global Sun Oven. The payback time for me was about ten years, but you know what? I've owned mine for 13. Also, my goal with saving energy isn't just to save money, it's to reduce my pollution footprint by consuming less resources. Finally, this thing is just plain fun to use.

Another company makes a bigger version that fits two pots side by side, and it's actually a little cheaper, than the model pictured, but it doesn't get quite as hot, and it's not nearly as convenient. (You have to do a lot of fiddling with the mirrored panels to set it up and to shut it down.) I know because I own one of each.

Use a crockpot or a microwave oven for baking. Besides a sun oven, these are the cheapest ways to bake.

Open the oven door only when necessary. Oven temperature drops 25-30 degrees every time you open the door. Getting an oven with an oven light and a glass window in the door will let you check on your food without opening the door.

Don't put aluminum foil on the bottom of a gas oven to catch drippings. The foil blocks the heat that the oven is trying to produce. (It's fine to put foil in an electric oven, as long as you leave the heating elements on the side exposed.)

Use glass and ceramic pans when baking. They retain heat better than metal pans and allow you to lower the baking temperature by 25 degrees.

Isolate the kitchen. If the oven is on for an hour or more, close doors leading to the kitchen to keep the kitchen from heating up the rest of the house. If you have a stove exhaust fan, use it.

Don't use pilot lights on gas burners. Pilot lights not only waste gas Cost24/7, they add heat to your home. Eliminating pilot lights means lower costs for cooling since you'll run the A/C less. Going pilotless will use 40% less gas than normal. (source) If your existing stove already has pilot lights, turn them off and use a clicker-lighter to light the burner when you're cooking. (Turning them off requires tightening the set screw. You can't just blow the pilot out, because then gas will still leak out the unlit pilot hole.)

Stovetop vs. microwave is about the same. While microwaves are more efficient than oven-baking, they're slightly less efficient than stovetop cooking, though the difference is so small it doesn't really matter which you use. (Home Energy)

Remember that if your goal is to save energy for environmental reasons, the real savings is by substituting vegetarian foods for meat, not by changing your cooking methods. It takes 68 times more energy to produce beef than to produce potatoes. (more...)

Temperature (degrees F) Electric oven Gas oven, electric 350°


Energy Used 2.0 kWh 0.112 therm +0.35 kWh


1 hr.


ignition Electric convection oven,


1 hr.



45 min. 1.39 kWh


The cost of baking methods compared The table at

Gas oven, pilot costs more

(but over 350° 1 hr. 0.112 therm 14¢

a year, since the pilot is always on)

right shows how different baking methods up. I stack suspect Toaster oven Microwave oven 350° High 1 hr. 0.33 kWh 4¢ 4¢ Crockpot 200° 7 hours 0.70 kWh 8¢

that the figure for electric might be ovens too

15 min. 0.36 kWh

high. I'll measure the actual use of an oven some

time and report it here.

Assumes 12¢/kWh for electricity and $1.25/therm for gas. All figures from Consumer Guide to Home Energy Savings, as reported by Home Energy 2005, except: (1) Toaster oven is by my own measurement; CCE gets 0.95 kWh for 425° @ 50 min. (2) I added the electrical use figure for the electric ignition Gas oven, as per Home Energy 1993. Time ratio of 4:1 for oven:microwave confirmed by Home Energy 2001.

Note from the second row in the table that gas ovens use electricity! Electric ignition ovens run a 350-watt glow bar to keep the gas flame going. (more...) APS has a good table showing the efficiency of gas, electric, and microwave ovens. The efficiency doesn't tell you the cost, though, because different energy sources are charged at different rates. Note that for someone baking three hours a week, the cheapest baking method saves only $2.61/mo. compared to the most expensive method. This underscores my point that focusing on cooking methods is not the way to save electricity, and you should look at heating, cooling, lighting, and laundry instead.

Induction ovens: Very efficient but super-expensive Induction stoves cook by heating the pot or pan directly. Oh, you thought that's what your current stove does? No, a regular stove starts with the heat elsewhere which is then transfered to the pot or pan. An induction stove doesn't transfer the heat to the cookware, it heats the cookware directly. Think of your cookware as having an invisible "on/off" switch that your stove knows how to activate.

Doesn't that just seem like magic or something? I could explain how that works, but let's not spoil the mystery.

Anyway, since it heats the cookware directly, induction cooking is more efficient—as you might expect. An induction stove uses a whopping 30% less energy than a regular electric stove. (It doesn't save anything on the oven, though, just the stovetop.) But keep your panties on, because the cheapest induction stove you can buy is $1300. If you use all four burners for half an hour a day on medium, five days a week, it will take only about 42 years to pay for itself. Congratulations. Oh, and did I mention that you can use only ferrous (iron or steel) cookware? Aluminum and copper won't work, so you might be looking at buying new cookware.

Now, there are other reasons you might like an induction stove. So here's the big list of possible pros:

It's magic! Okay, it's not really magic, but as Arthur Clarke said, any sufficiently advanced technology is indistinguishable from magic.

You get the instant change of temperature that you'd get with a gas stove, but without the fumes.

It doesn't add extra heat to your home, since all of the heat used is for cooking, with no extra wasted.

The cooktop cools down very fast when you turn it off—about four times faster than a conventional cooktop.

The surface is flat and seamless, so it's easy to clean (although many electric stovetops offer the same convenience).

It does save energy, if being green is more important to you than a really high price.

For more than you ever wanted to know about induction ovens, see The Induction Site and this article in Popular Mechanics.

Efficiency: probably not what you're thinking Most people who ask me which fuel source is "most efficient" have it backwards: They actually want to know what's cheapest. But efficiency and cost are not the same

thing. Efficiency is what percentage of a fuel goes towards doing work. Electric ranges are a lot more efficient than gas, but gas is very cheap, so overall it's usually cheaper to use gas even though it's not as efficient as electric. Energy used by electric ovens The specs I've seen for electric ovens have a bake element of 2000 to 3500 watts with a maximum temperature of 500-550° F. However, different ovens should use about the same amount of energy to come up to and maintain a given temperature setting. My feeling is that the higher-wattage ovens simply get up to the desired temperature faster, but don't take any more energy to do so. And whether the oven is high-wattage or low wattage, it's rare for the bake element to run continuously at full capacity. It either runs at a lower power level or shuts itself off for a few minutes at a time in order to maintain the desired temperature. Estimates I've seen elsewhere for an electric oven set to 350° is 2.0 kWh per hour, regardless of the wattage of the bake element. I suspect that this might be a bit high, and I'll do a direct measurement myself when I have time. (I did measure consumption in a toaster oven at 350° and

it used only 0.33 kWh in an hour.) In the meantime, if you're using the 2.0 kWh figure for an oven, adjust up or down for higher or lower temperatures. Broil elements are rated higher than bake elements, typically 3000 to 3600 watts. However, it's unlikely that they run continuously to maintain temperature, so I think a figure of 2400 watthours per hour is a more reasonable figure to use while broiling. Self-cleaning ovens use energy at a much higher rate when cleaning, because they get much hotter than they do for cooking. I couldn't find any reliable figures for the rate, but the Department of Energy says that an oven uses about 5.3 kWh per cleaning cycle.

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