RENEWABLE ENERGY FAQs

What is renewable energy?
What are some common forms of renewable energy?
What are some advantages of using renewable energy?
What's the connection between renewable energy and hydrogen and fuel cells?
Isn't renewable energy too expensive to be commercially viable?
Can I meet all my energy needs with renewable energy?
Do wind turbines kill birds?
Where can I find out about renewable energy dealers, sales, installation and equipment?
Can you recommend an installer or supplier for a renewable energy system?
How much do any of these renewable energy systems cost, and how much will I save on utility bills?
Is there any financial assistance available for installing renewable energy systems?
Is it a good idea to buy online?
What does "energy conversion efficiency" mean?
Can I really use renewable energy to power my home or business?
Can I install it myself?
When will renewable energy replace coal and nuclear power plants?
What are the environmental benefits of renewable energy?
What are the disadvantages to using solar and renewable energy?

What is renewable energy?
Renewable energy is electricity that is produced from sources that replenish themselves naturally. This includes wind, sunlight (solar), landfill and agricultural waste (biomass), the heat of the earth (geothermal), and eligible hydro-electric facilities.

These renewable sources of electricity have less impact on the environment than traditional methods of electricity generation, which includes burning fossil fuels such as coal, oil and natural gas. Natural gas and coal, for example, are not renewables because their use consumes gas and coal reserves at a much quicker rate than they are replenished.

Renewable energy has a much lower impact on the environment than traditional methods of electricity generation. It produces lower levels of air pollutants, wastewater, smog and acid rain, and it can help reduce greenhouse gas emissions. By supporting renewable energy, you can help protect the environment by offsetting the need for more fossil fuel generation. In addition, renewable energy can help reduce our nation's reliance on fossil fuels.

What are some common forms of renewable energy?
Ultimately, all renewable energy used on earth is solar energy. Solar thermal energy and photovoltaic devices make direct use of solar radiation, but wind, hydroelectric, and biomass energy are also driven indirectly by the sun. Geothermal energy is technically nonrenewable, as it is driven by limited steam reservoirs in the ground, but it is usually classified as renewable due to its wide perception as a clean way to generate electricity.

What are some advantages of using renewable energy?
Petroleum and natural gas are expected to become scarce in the coming decades. Coal and uranium offer longer-term energy supply, but they too will eventually run out. In addition, all of these fuels produce environmental impacts that threaten our health and quality of life. Renewable energy sources are clean and will not run out in the foreseeable future. Because of their consistent long-term availability, renewable energy resources are also inherently more stable in price than fossil fuels. Many renewable energy technologies are modular and portable, making them practical anywhere from a city center to a remote mountaintop. And renewable energy is naturally decentralized, offering us a safer and more robust alternative to today's giant-scale power plants and their vulnerability to fuel price swings, natural disasters, and terrorism.

What's the connection between renewable energy and hydrogen and fuel cells?
At SERC, we specialize in developing systems that integrate renewable energy with hydrogen and fuel cells. Renewable energy is naturally intermittent. Hydrogen provides a means to store renewable energy for times when the sun doesn't shine or the wind doesn't blow. When these resources are available, they can be used to generate electric power for immediate use, with surplus energy being converted to hydrogen using an electrolyzer. The hydrogen is stored until renewable energy is unavailable, at night or on cloudy or windless days. A fuel cell then converts the stored hydrogen to electric energy. Hydrogen thus offers a solution to renewable energy's key deficiency, i.e. that it's not always available when we need it. To learn more about the connection between renewable energy and hydrogen and fuel cells go to the solar hydrogen cycle web page.

Isn't renewable energy too expensive to be commercially viable?
On a dollars-per-kilowatt-hour basis, renewable energy is still generally more expensive than fossil fuels, although its cost is decreasing all the time. In some energy markets, new wind turbines are already less expensive than new conventional power plants. As fossil fuels become scarcer in the future, renewable energy will be more economically attractive. While recent growth in the renewable energy industry is in part due to government and utility incentives, it must be noted that conventional fuels also benefit from direct and indirect subsidies, including externalization of the social costs created by polluting power plants.

Can I meet all my energy needs with renewable energy?
It is feasible for most homes to generate all or most of their energy on-site using photovoltaics and other technologies. However, bear in mind that a dollar spent on making your home more energy efficient is money better spent than the same dollar putting solar modules on your roof. If you are considering installing renewable energy equipment, work first to make your home as energy efficient as possible.

Renewable-powered transportation is another matter. In wealthy countries, where nearly every household owns at least one car, it is probably not realistic to anticipate that renewable energy will enable us to continue with business as usual. A more modest and efficient transportation system might be sustainably run on renewable energy.

Could we really run our whole global economy on renewable energy?
The same point holds true on a global scale -- the more energy-efficient we make our society, the more feasible it will be to convert to an all-renewables economy. "Sustainable" as renewable energy may be, it cannot indefinitely support unsustainable growth in global energy consumption. Wealthy countries have the most room for improvement: per capita energy consumption in the U.S. is six times that of the rest of the world, and over ten times greater than in developing countries. Some good news: the surface of the Earth receives ten thousand times as much solar energy each year as is consumed by all human activity.

Is it true that a photovoltaic module can't generate as much energy in its lifetime as it took to manufacture it in the first place?
This claim is often heard from renewable energy skeptics. If true, it would put the sustainability of PV power in considerable doubt. A study by the National Renewable Energy Laboratory, however, determined that PV modules require only one to four years to produce the total energy consumed in their manufacture, depending on the type of module. Comparing this to an expected 20- to 30-year module life expectancy suggests that PV module production is a net energy generator. The Solarex Corporation built a photovoltaic-powered "breeder" PV module manufacturing plant in Frederick, Maryland in 1982, demonstrating how PV power can be truly self-sustaining.

Do wind turbines kill birds?
This is another area of concern for people who worry that renewable energy is not as sustainable as it's made out to be. It has been documented that certain types of wind farms can present a hazard to some species of birds, depending on location and other factors. However, wind turbine and tower designs are evolving to address this issue by reducing rotational speeds and eliminating tower features that make the turbines attractive places to roost. Siting of new wind farms takes bird habitat and migration routes into account. It's worth noting that vehicles reportedly kill over 1,500 times as many birds in the U.S. each year as do wind turbines.

The underlying point raised by these last questions is a valid one: all means of producing energy have some environmental impact. Scientists and engineers need to keep working to minimize these impacts through technical solutions, but the real onus is upon the rest of us to use energy efficiently and wisely.

Where can I find out about renewable energy dealers, sales, installation and equipment?

Two places to begin:

• The sponsor links nearby will give you quick access to valuable internet addresses and emails.
• If those don't get you what you want, check your local phone book. You may find that installers are busy these days.
• You can also consult our directory for more sponsors and other organizations.

Can you recommend an installer or supplier for a renewable energy system?

No, the Solar Guide is meant to be an objective information portal. However, we have carefully checked our advertisers and sponsor links and you can be sure that they are well-run, reputable businesses. We wouldn't let them advertise with us, otherwise.

How much do any of these renewable energy systems cost, and how much will I save on utility bills?

There is no single or simple answer, even if you are only talking about one kind of energy, such as solar. Some short answers we can give here:

• They are all definitely in the thousands.
• Solar and renewable energy rebates as well as other incentives can reduce the cost of any RE system.
• The size of the system is of course a factor.
• For solar thermal and solar pool heaters, you have to consider the price of the fuel used to back up the system.
• The price of other sources of energy will continue to rise, so who knows how much money you will save in the future?
• It also depends on how much you pay your utility for electricity or natural gas, and how much your utility will pay you for any excess power (with net metering) that you generate with your solar system.
• You can ask your renewable energy system provider how much your new system will produce on an annual basis and compare that number to your current annual electricity or hot water demand to get an idea of how much you will save.

Is there any financial assistance available for installing renewable energy systems?

In the US, you can check the DSIRE database to find out all local, state and federal incentive programs.

In Canada, the federal government's Office of Energy Efficiency has a grant program, the Home Energy Efficiency Retrofit Grants, to encourage home energy efficiency. To be eligible, your home must undergo an EnerGuide for Houses Evaluation. To qualify, you must contact an energy evaluator then follow their evaluation recommendations, and you must achieve a minimum improvement. Natural Resources also lists other incentives.

Is it a good idea to buy online?

Yes — if you know the company is reputable and if they offer secure online transactions. Sites that advertise with the Solar Guide have been checked out for reputability and service. Check the site for certifications with companies such as Thawte or other security certification sites.

What does "energy conversion efficiency" mean?

Energy conversion efficiency is an expression of the amount of energy produced in proportion to the amount of energy consumed, or available to a device. The sun produces a lot of energy in a wide light spectrum, but we have so far learned to capture only small portions of that spectrum and convert them to electricity using photovoltaics. So, today's commercial PV systems are about 7% to 17% efficient, which might seem low. And many PV systems degrade a little bit (lose efficiency) each year upon prolonged exposure to sunlight. For comparison, a typical fossil fuel generator has an efficiency of about 28%. (from EERE.gov)

Can I really use renewable energy to power my home or business?

Many renewable energy systems can be compatibly blended with the regular electricity provided by your local utility. This is called grid integration and it is increasingly popular around the world and in the USA.

Can I install it myself?

Maybe — if you are a pretty good electrician. You would be better off seeking out a licensed installer who knows all the ins and outs of electricity, codes and regulations in your area.

You are also likely to void warranties if you self-install. And don't forget that electricity can be very dangerous.

When will renewable energy replace coal and nuclear power plants?

Right now, at least in North America, nuclear and fossil-fuel-based energy is still quite inexpensive compared to solar and wind energy. However, the price of fossil fuels is continuing to rise and the price of solar and renewable energy continues to decline. Peak oil production is right around the corner, and people are increasing their demand for clean energies.

In Japan, Germany and some developing countries, renewable energies are already competitive due to a number of market forces. These same market forces are becoming increasingly relevant to consumers in North America (i.e. the high price of fossil fuels, increasing government incentives and concern for global warming, to name a few).

What are the environmental benefits of renewable energy?

Every kilowatt-hour of electricity produced by a renewable energy system displaces the same amount of electricity produced by conventional power generation stations that are using fossil fuels that contribute to CO2, SO2, NOx and smog. Clean renewable energy production reduces suspended particulates we usually call smog, which are a significant health problem on the same hot sunny days when (for example) a solar energy system can produce electricity at its peak level.

What are the disadvantages to using solar and renewable energy?

The biggest disadvantage and the only truly significant one remains the cost. For example, solar energy technologies require a significant initial outlay. Still, in nearly all cases, this high initial cost is recovered through substantial fuel savings over the life of the product (15-30 years), and solar energy systems can last much longer than this. But in areas where there are no hydro wires, choosing solar is as obvious as the sun in the sky.

SOLAR ENERGY FAQs

Photovoltaic (Solar Electric) System Basics
What is a photovoltaic (PV) system?
What's so special about photovoltaics (solar electricity)?
Can a PV system be installed at a residence?
Does a PV system replace an electric utility?
What are the benefits of having a PV system?
How much electricity can a PV system produce?
What is the lifespan of a PV system?
What is involved in maintaining and operating a PV system?
How can I finance the cost of a PV system?
Is there a difference between solar thermal and solar water heating?
Why would I choose solar thermal or solar water heating?
What is the best solar thermal system?
How many solar thermal panels would I need to heat water for my home?
What is the difference between solar thermal and photovoltaics?
How does the conversion of solar energy to heat in a glycol-based system work?
Do you really think solar and renewable energies are a good investment?

What is a photovoltaic (PV) system?
Photovoltaic (PV) systems (or solar electric systems) use PV cells to convert sunlight into direct current (DC) electricity. PV cells are made from silicon and were originally developed to power spacecraft and space stations. The cells come wired together in panels that typically measure about 4 feet by 1 foot by 1.5 inches deep. A group of panels mounted on a frame is called a PV array.

To provide electricity reliably and safely, PV systems include several pieces of equipment in addition to the PV array. This balance of system components typically includes a charge controller, an inverter, wiring, and a form of electricity storage (typically batteries).

Most PV systems convert the DC electricity that is produced by the solar panels into the common household form of electricity—alternating current (AC)—by using an inverter. AC electricity can then be used to power your appliances directly, or feed back to an electric utility's grid. The DC electricity can also be stored directly in batteries for later use. In this case, to prevent overcharging or discharging of the batteries, a charge controller is used. Instead of an AC inverter, a DC converter can be used to convert AC electricity coming from the utility grid into DC electricity, which can then be stored in batteries for use during power outages. This type of configuration is often called a PV uninterruptible power supply (UPS).

What's so special about photovoltaics (solar electricity)?
Photovoltaics has received attention from researchers and the private sector because, unlike traditional power generation sources, these technologies produce electricity using a renewable source—the sun—without creating noise, emitting pollutants that cause climate change such as smog and acid rain, or polluting our water resources. Even when the emissions related to solar cell manufacturing are counted, PVs produce less than 15% of the carbon dioxide from a conventional coal-fired power plant. In fact, using solar electricity to power a million homes would reduce carbon dioxide emissions by 4.3 million tons per year, the equivalent of removing 850,000 cars from the road (Source: EPA).

Can a PV system be installed at a residence?
Yes. PV panels can be installed as modular systems on existing homes, or built into rooftop material for new homes.

Does a PV system replace an electric utility?
PV systems are typically used as either stand-alone systems or grid-connected systems. The role of photovoltaics in these two types of systems is very different, and the design decisions and performance requirements are very different as well.

Stand-alone PV systems generate all of the on-site electricity needs of a home. Therefore, they are not connected to any electric utility. Stand-alone systems can provide AC or DC electricity, and typically include batteries to store electricity for use when the sun is not shining. Stand-alone systems are often cost-effective when installed in remote areas where access by electric utilities is difficult and expensive.

Grid-connected PV systems are typically sized to meet 50% or more of a home's electrical load. These systems are not always sized to meet all of the electricity loads of a house because of the higher up-front costs associated with purchasing a larger system. A larger system will cost less per kilowatt-hour generated due to the economies of scale associated with manufacturing processes. Thus, a grid-connected system will generate all or part of the electricity required in a home, while the remaining electricity loads are met by the utility.

PV systems can be easily integrated with a utility's electrical grid providing clean, renewable electricity for homeowners, while still ensuring continuous power supply from your regular utility.

What are the benefits of having a PV system?

Reduce your utility bill
It's generally too expensive to create a PV system to power everything in a house. However, if used wisely, PV systems can significantly reduce your utility bill. Any energy produced for "free" by the sun and your PV system is energy that you don't have to purchase from your utility. This translates into direct savings on your monthly utility bill.

In addition to the direct savings, the PV arrays also act as a sunshade for your roof, reflecting heat from the sun that would otherwise be absorbed by your house. A shaded roof area can reduce the air temperature of your house, reducing the energy required by your air-conditioner to keep a comfortable temperature in your home.

Environmental responsibility
Another important consideration in installing PV systems is environmental responsibility. By using a renewable power source, you're helping reduce the impact of energy use on the environment for generations to come.

Improved power reliability
If you use a grid-connected system with battery banks, then you can be assured of a continuous power supply in case of a power outage.

How much electricity can a PV system produce?
In California, the average residential customer uses 6,500 kilowatt-hours (kWh) of electricity per year (as listed in the California Energy Commission's Buying a Photovoltaic Solar Electric System, A Consumer Guide. A 2-kilowatt (kW) PV system installed in Santa Clara, on average, can produce about 3,700 kWh of electricity annually. This is about one-half the load of a typical California customer depending on the geography and climate.

EXAMPLE:
Given a 2-kW rooftop PV system located in the Santa Clara region, where the average number of full hours of sunshine per day is 5.1 hours, the amount of electricity that this system could potentially produce is:

= 2 kW x average annual sunshine hours
= 2 kW x (5.1 hrs/day x 365 days/year)
= 3,723 kWh annually

Note: the rated output of PV modules is assessed using the full hours of sunshine per day where one (1) full sun hour is defined as being exposed to a solar intensity equal to 1000 watts per square meter. Full sun hours does not indicate the number of hours that the sun is shining in a day, but rather is an indication of the intensity of the sun.

Also important to note is that not all of the sunshine that strikes a PV cell will be converted into electricity. For the above example, let's assume a derating factor of 0.75. This factor accounts for inverter efficiency and wire losses, but it does not include battery losses. Thus, the amount of electricity that a 2-kW system located in the Santa Clara region could potentially produce is:
= 3,723 kWh x 0.80
= 2,978 kWh

If a system includes battery banks, then an additional derating factor must be considered in the above calculation.

This amount of electricity represents an annual cost savings of:
= 2,978 kWh x 7.5¢/kWh
= $223 per year, or almost $19 per month.

What is the lifespan of a PV system?
Solar Electric systems last a long time depending on the amount of active use, or the amount of sunshine converted into electricity by the PV cells. Most systems are only in use for 6 to 8 hours per day. Manufacturers will usually provide 10 to 20-year warranties, but PV modules will likely last longer than that. The balance of system components, however, will have a shorter life.

What is involved in maintaining and operating a Solar Electric system?
Without any moving parts, maintaining a PV system is relatively simple. For grid-connected systems, minimal maintenance is required, including keeping the panels free of any debris such as fallen leaves, bird droppings, etc.

For stand-alone systems, the batteries usually require the most maintenance. Contact your PV system retailer for more information on maintaining battery banks.

PV system manufacturers will usually provide a 10- to 20-year warranty on the PV modules, and a 5- to 10-year warranty on the balance of system components.

How can I finance the cost of a PV system?
Once you've considered the economics of installing and operating a PV system, and are interested in purchasing a system for your home, you should then consider all the financing options that are available to you.

Is there a difference between solar thermal and solar water heating?

Yes. The Solar Guide uses solar thermal as a catch-all term, but it is important to note that solar thermal and solar water heating fall into three or more very different types of systems:

• Solar thermal water heating systems heat water for your home. They do this using heat exchange or by directly heating the water. For more information, see The Solar Guide's section on solar thermal.
• Solar pool heating heats water for your pool or hot tub. See our section on solar pool heating.
• Solar thermal also applies to solar floor heating and space heating.

Why would I choose solar thermal or solar water heating?

Solar thermal and other solar water heating systems (solar pool heating) are easy to install and can work year round to heat water for your home. These systems pre-heat your water before it enters your hot water tank or pool. Free heat of the sun (year round) gives you significant savings on your energy bill.

Solar water heating systems cost between $3,500 and $5,000 installed, depending on the type of system you choose. These can reduce your hot water heating bill by up to $100 per month, depending on how much you use and where you live. The payback period for an investment in a solar thermal water heating system is three to five years. After that, the savings are all yours and systems have been known to last longer than twenty years.

What is the best solar thermal system?

"Best" is a relative term. We'll answer your question in terms of most practical, most reliable or most energy efficient, but these all depend on where you live.

For any climate where it freezes, the use of a closed loop glycol-based solar thermal system might be the only practical choice. A solar thermal drain-back system is also used under these conditions, but these are not as popular because they are not quite as reliable.

For warmer climates, the most energy-efficient system is a system called thermosiphon. It requires no electric pumps to operate (in technical terms, this makes it a passive solar thermal system). The sun heats the fluid until it rises to the top of the panels, where it flows into a tank or heat exchanger. From the heat exchanger, only the hottest water is skimmed off from the top of the tank as you draw down the hot water.

How many solar thermal panels would I need to heat water for my home?

You can get the best answer to this by contacting a solar thermal dealer. This will depend on how many people in your household, on how much hot water you use and how much sunlight you receive.

However: a typical family of four might require four square meters, and we can roughly guess that a square meter per person is a fairly accurate estimate. But don't hold us to that!

What is the difference between solar thermal and photovoltaics?

Solar thermal systems generate heat (for water or air) with the radiation of the sun.

A solar photovoltaic system uses solar radiation to generate electricity.

How does the conversion of solar energy to heat in a glycol-based system work?

Solar radiation hits the absorber (solar thermal panel) and is then transmitted to the heat transfer medium (glycol, usually) and converted to heat. The vacuum plus the insulation provided by layers of the absorber assure that heat remains in the solar thermal system.

Solar thermal systems with glycol use a composite tube that is made up of a jacket tube and absorber tube. Since these are made completely of glass, they are well-protected against degradation.

Do you really think solar and renewable energies are a good investment?

Solar energy, solar thermal and other forms of renewable energy will become cheaper, as people continue to invest in them. As people invest in them, this will drive down the cost-- as it already has (significantly) over the last few decades.

This has a snowball effect: the technology becomes more usable, cheaper and convenient.