Frequently Asked Questions
Energy Efficiency and Renewable Energy
A Net Metering agreement allows you to use the electricity you generate first, reducing what you would normally buy from your utility or ESP. If you generate more electricity than you use, the excess goes through your electric meter and into the grid, spinning your meter backward. Your meter shows the net amount, measured as the difference between the electricity you generate and the electricity you purchase from your utility or ESP.
Renewable energy technologies are labor intensive. Jobs evolve directly from the manufacture, design, installation, servicing, and marketing of renewable energy products. Jobs even arise indirectly from businesses that supply renewable energy companies with raw materials, transportation, equipment, and professional services, such as accounting and clerical services.
In turn, the wages and salaries generated from these jobs provide additional income in the local economy. Renewable energy companies also contribute more tax revenue locally than conventional energy sources.
The economic advantages of renewable energy also extend far beyond the local economy. The whole country benefits. In 1997, the United States spent about $65 billion dollars outside the country to pay for fossil fuels. But as one of the world leading manufacturers of renewable energy systems, we can bring in more money with the increased use of renewable energy sources around the world. Currently, for example, the United States manufactures about two-thirds of the world photovoltaic (PV) systems. And it exports about 70% of these PV systems, mostly to developing nations, resulting in annual sales of more than $300 million.
U.S domestic oil production has been declining since 1970. In 1973, the United States only imported about 34% of its oil. Today, our country imports more than 53%, and it is estimated that this could increase to 75% by 2010.
Most of the world oil reserves are now in the Middle East. We have witnessed this shift in economic influence through the last three sharp increases in the world oil prices: the Arab Oil Embargo in 1974, the Iranian Oil Embargo in 1979, and the Persian Gulf War in 1990. It has resulted in periods of negative economic growth and a rising trade deficit.
But with renewable energy, we can decrease our dependency on foreign oil imports. For example, the U.S. Department of Energy estimates that if we displace 10% of our petroleum use for transportation with biofuels, which are produced from organic material, we could save about $15 billion from 2000 to 2010. A 20% displacement could save us about $50 billion from 2010 to 2030. This would strengthen our energy security, as well as our economic and national security.
In most states, on the anniversary of your agreement, you will be billed for the net electricity you consumed for the previous twelve months. You may request the option of monthly billing. Depending on the type of agreement you have, your meter might show a credit during some or all billing periods, even though the actual kilowatt-hours you generate and consume are equal.
Your utility is usually not required to pay you or credit your account for your excess generation each year, but it might do so. Contact your utility or ESP to discuss the option of negotiating rates for purchasing excess generation. If your current utility or ESP does not purchase excess electricity, you may contract with another company that will agree to purchase it.
The total daily Irradiation (Wh/sq-m) is calculated by the integration of the irradiance values (W/sq-m).
Click here for solar radiance maps of the US.
CSP’s relatively low cost and ability to deliver power during periods of peak demand—when and where we need it—mean that CSP can be a major contributor to the nation’s future needs for distributed sources of energy.
For more information, please go to http://www.eere.energy.gov/solar/csp.html
Net metering allows your electric meter to go backwards when you are producing more electricity than you are using.
Essentially, it indicates how much electricity you pulled from the grid rather than the amount of electricity that you used.
PV cells are typically combined into modules that hold about 40 cells; about 10 of these modules are mounted in PV arrays that can measure up to several meters on a side. These flat-plate PV arrays can be mounted at a fixed angle facing south, or they can be mounted on a tracking device that follows the sun, allowing them to capture the most sunlight over the course of a day. About 10 to 20 PV arrays can provide enough power for a household; for large electric utility or industrial applications, hundreds of arrays can be interconnected to form a single, large PV system. (VBE Note: One of our services is to determine how much PV can be installed at your site and to determine what such a system can accomplish toward meeting your electrical needs.)
Some PV cells are designed to operate with concentrated sunlight. These cells are built into concentrating collectors that use a lens to focus the sunlight onto the cells. This approach has both advantages and disadvantages compared with flat-plate PV arrays. The main idea is to use very little of the expensive semiconducting PV material while collecting as much sunlight as possible. But because the lenses must be pointed at the sun, the use of concentrating collectors is limited to the sunniest parts of the country. Some concentrating collectors are designed to be mounted on simple tracking devices, but most require sophisticated tracking devices, which further limit their use to electric utilities, industries, and large buildings.
The performance of a PV cell is measured in terms of its efficiency at turning sunlight into electricity. Only sunlight of certain energies will work efficiently to create electricity, and much of it is reflected or absorbed by the material that make up the cell. Because of this, a typical commercial PV cell has an efficiency of 15% – about one-sixth of the sunlight striking the cell generates electricity. Low efficiencies mean that larger arrays are needed, and that means higher cost. Improving PV cell efficiencies while holding down the cost per cell is an important goal of the PV industry, NREL researchers, and other U.S. Department of Energy (DOE) laboratories, and they have made significant progress. The first PV cells, built in the 1950s, had efficiencies of less than 4%.
Solar electric (PV) systems typically do not require maintenance, other than periodic cleaning of the solar panels. PV panel life is typically 25 years. If you have a battery system, the batteries may require periodic maintenance such as “equalization” or water topping off.
The more efficient use of energy throughout our country results in less money spent on energy by homeowners, schools, government agencies, businesses, and industries. The money that would have been spent on energy can instead be spent on consumer goods, education, services, and products. For more information, see the American Council for an Energy-Efficient Economy and the Alliance to Save Energy Web sites.
An energy-efficient economy can grow without using more energy. In 1998, for instance, the U.S. gross domestic product increased 3.9%, while U.S. energy use decreased by 0.3%.
High Electric Bill Analysis
What we can do is to instrument your occupancy in order to determine where every last drop of electricity goes. This, in combination with an analysis of your electric bills, will usually pinpoint the problem(s). We can then recommend cost-effective solutions.
A fixed fee of $250 includes a review of electric bills, instrumentation of your major energy users, analysis of the data and recommending a solution.
A fee based upon the amount of savings we can produce. We do the same review, instrumentation and analysis, but this time you only pay if we achieve savings. Your obligation is to implement all cost-effective solutions, then pay us half your electrical savings for the first year of operation. So if we can cut your bill by $200/month, then you would owe us $1200 for the service.
Photovoltaic System Design
If you have a design from someone else, you can check whether the design has been certified by the Florida Solar Energy Center. The FSEC PV Division provides a certification service to manufacturers and distributors. The FSEC website is listed under Resources. Dr. Messenger, our Vice President for Engineering, has designed more than 50 PV systems that have been approved by FSEC.
If your design is not FSEC-approved, you can submit it to FSEC for approval or you can have us review it for code compliance and for proper use of components.
Photovoltaic System Installation
When we install a battery-backup PV system, because so many owners already have small gasoline generators, we always install a transfer switch that will enable the generator to provide backup power for charging the PV system batteries in the event of cloudy weather. But, in this case, the fossil generator only needs to be run a few hours a day to charge the batteries. As a result, considerably less fuel is used and the noise and pollution associated with fossil generation are limited to a few hours a day, if any.
In our area, our first 10 installations were battery-backup systems. We are now installing some non-battery-backup systems where they make sense to the owners. In effect, battery-backup systems involve betting on whether a hurricane will strike, although some of our system owners have already benefited from battery-backup systems during power outages from causes other than hurricanes.
Some try to do a payback analysis on battery-backup systems. In fact, no one does a payback analysis on fossil-fueled generators, because if they were to do so, it would be found that the system does not ever pay for itself in terms of the electricity it generates. It is just there as a convenience. The same is true of the battery-backup portion of the cost of a PV system—it never pays for itself. But it is a highly-desirable form of emergency power. So the payback analysis needs to be done on the non-battery backup part of the system.
Depending upon available incentives, it is possible that a residential PV system will pay for itself in less than 10 years. Then for the next 20 years or more, it makes free electricity. Since commercial incentives and electric rates differ from residential incentives and rates, commercial economics can be even more attractive than residential economics.
As of July 1, 2006, the State of Florida has introduced a program of rebates for grid-connected PV systems. Qualifying systems are eligible for a rebate of $4 per watt, up to $20,000 for a residential installation and $100,000 for a commercial installation. To qualify for the rebate, the system must be at least 2000 watts and must be installed by a licensed electrical or solar contractor and must be permitted and inspected before the utility will allow the interconnection.
Rebate request forms are available on line at http://www.fsec.ucf.edu/energynews/2006/2006-04-draftrules.htm.
For more details on the rebate rules, go to http://www.fsec.ucf.edu/energynews/2006/2006-04-draftrules.htm.
Federal Tax Incentives
As of January 1, 2006, a tax credit of 30% is available on residential PV systems, up to a maximum of $2000. More information is available at http://www.fsec.ucf.edu/EPAct-05.htm.
In addition to a straight 30% tax credit, commercial incentives are based upon depreciation and other considerations. More information is available at http://www.fsec.ucf.edu/EPAct-05.htm.
Prior to 2002, stand-alone PV systems were the most common, but since 2002, more PV generation has been attributed to grid-connected systems than to stand-alone systems. One reason for this transition is that fully-interactive, grid-connected, systems optimize the use of PV electricity. The reason for this is that when the grid is available for a fully interactive grid-connected PV system, none of the energy generated by the PV system is wasted. Any electricity generated by the PV system that is not used on site is sold back to the utility for someone else to use.
Grid-connected, but not interactive, PV systems use the utility grid as an auxiliary battery charger. This kind of system is common in areas where the grid connection is only available for a few hours each day. The grid provides additional battery charging to supplement that provided by the PV system. These system do not SELL energy to the grid. They just purchase it when it is needed and available. The system batteries store the purchased or PV energy for later use. If excess PV energy is produced, it is wasted.
Fully interactive grid-connected systems can either purchase energy from, or sell energy to, the utility grid. Any utility interactive system that is programmed to sell electricity to the grid must meet very stringent UL listing requirements. These systems must be capable of monitoring the condition of the utility grid and automatically disconnecting from the utility grid if the utility grid shuts down. There are two types of fully interactive grid-connected PV systems, as shown in Figure 1.
Figure 1a shows a utility interactive PV system without battery backup. Whenever the sun is shining and the utility grid is powered up, the electricity produced by the PV system is first used by the system owner and any leftover electricity is sold back to the utility grid. If the grid goes down, the PV system must also shut down. When this happens, the owner of the system will be without PV-generated electricity until the grid comes back on again.
Figure 1b shows a utility interactive PV system with battery backup. This system combines the best features of the stand-alone and the grid-connected systems by incorporating an emergency power output feature on the system inverter that continues providing power to selected circuits if grid power is lost. One set of terminals on the system inverter connects to the utility grid through the owner’s main circuit breaker panel. The other set of terminals connects to emergency loads. When grid power is available, this set of terminals will either send excess PV power back to the main circuit breaker panel or will use grid power to supply the emergency loads at night. If grid power is lost, this section of the inverter shuts down, but the emergency terminals of the inverter remain operational. When the sun is shining, power produced by the PV array is used for meeting the requirements of the emergency loads and for battery charging. As long as there are enough batteries, and as long as the PV system generates enough energy each day to meet the needs of the emergency loads, the emergency loads will be operable 24 hours a day while the utility grid is out. When the grid is restored, the system automatically reconnects to the grid and resumes normal operation.
Additional redundancy can be achieved with a PV system for cloudy days. If a fossil fuel generator is incorporated into the system, then the generator can be used to charge the batteries on cloudy days. The nice thing about this setup is that the generator will probably only need to run about 3 – 5 hours a day to provide any charge not provided by the sun.
Keep in mind that a fossil fuel generator CAN NEVER PAY FOR ITSELF, since it is only run when the utility is down. On the other hand, a utility interactive PV system will produce electricity every day over its lifetime, which can be expected to exceed 25 years. The PV modules in every system we install come with 25-year warranties. Depending upon the rebates or tax incentives available, the systems will pay for themselves before their lifetime is over. Furthermore, a 5000-watt PV system will eliminate the production of approximately 175 tons of carbon dioxide over a 25-year period.
The choice of a noiseless, pollution-free PV system, along with State and federal (and, perhaps, utility) incentive programs, can result in the system paying for itself in less than its lifetime. After the system pays for itself, it will be making money for you through savings on your electric bills.
When we design and install a system, we also:
- ensure that the systems meet all local and national code requirements,
- assist in preparation of all paperwork involving the electric utility interconnect agreement, permitting, Florida PV rebates and warranties,
- make sure the system will be aesthetically pleasing,
- teach our system owner how to optimize the performance of their system,
- verify that the system performs as advertised, prior to accepting final payment
The power available from a PV system depends on the Power Rating of the Inverter. Our battery-backup systems generally use either Outback 3600 W inverters or Xantrex 4000 W or 6000 W inverters. Note that this power is NOT the same as the power rating of the PV array. The PV array POWER determines the amount of ENERGY that the system can deliver in a day.
So the system POWER is important, because it determines how many and what types of emergency loads can be run simultaneously without overloading the inverter.
The system ENERGY is important, because it determines how long a particular combination of loads can be operated each day without using up all the electricity produced during that day by the PV array.
In particular, older appliances generally use a lot more ENERGY than newer appliances, so it may make good economic sense to replace an old refrigerator with an Energy Star unit, rather than to install a larger PV system to run an inefficient refrigerator. In many areas, either the State, federal government or utility may have incentive programs to encourage the purchase of more efficient appliances.
The following table lists common loads that might get priority under emergency conditions. Add the watts to ensure that your inverter will not be overloaded and add the kWh to be sure your system will generate enough electricity to meet your needs.
|Load||Approx Watts||Time On||kWh used|
|Energy efficient refrigerator||300||1 day||1.5 – 2.5|
|Microwave oven||600||10 min||0.1|
|Small fan||50||10 hr||0.5|
|Compact fluorescent bulb||15||5 hr||0.075|
|Hair dryer||1200||5 min||0.1|
|Clothes Washer||500||30 min||0.25|
|Laptop computer plugged in||50||1 hr||0.05|
|Desktop computer||200||1 hr||0.2|
|Small TV||100||1 hr||0.1|
|VCR or DVD Player||50||2 hr||0.1|
|Cell phone battery charger||5||4 hr||0.02|