SolSource team installs a PV array on a garage roof in Denver. Seth Masia photo.

Solar energy technologies are simple, but installing an array is a complex job, calling for both for technical expertise and ability to navigate the thicket of permits and incentives to get your project approved and financed. Choose an installer in much the way you’d choose a contractor for any major construction project. Here are some things to consider:

1. Is your installer eligible for the state or local incentives you want to use? Rebates often are paid only to projects installed by approved personnel. The State of California approves rebates only on systems using modules and inverters on an approved list, and constructed by installers on an approved list. The New York State Energy Research and Development Authority maintains a list of about 120 “eligible” installers for projects it partially funds, with another 90 names on a “provisional” list. Pennsylvania’s Sunshine Program has its own list of approved installers. You can work with a local installer who’s not on the list, but you won’t be eligible for the program in question. When talking installers, be sure to ask which incentive programs they have access to and how that will affect your financing options.
2. What’s the track record? How long has the company been in business, how many systems have they installed, and how happy are the customers? A reputable business should be happy to put you in touch with satisfied customers. Attend a meeting or two of the local ASES chapter (see page 10) and ask people there which installers have a solid reputation. Finally, look around the neighborhood for solar arrays, and ask the owners about their experience with the installer.
3. Consider whether you want to go with a very large regional or national organization, with a deep field of expertise and a sophisticated inventory and delivery infrastructure, or with a friendly and responsive local installer who may be able to answer an emergency phone call after a tree falls on your roof in the middle of the night. The large company may offer a better initial price due to economies of scale, but may be slower to respond to warranty and service issues later on. The local family-owned company lives on its reputation for service.
4. It’s smart to contact three promising candidates and call for estimates from each. Expect to spend an hour with each estimator.
5. Check with your homeowner’s insurance agent to find out whether there will be an extra charge to cover a new array against hail or wind damage

Estimating the job

Even before providing an estimate, an installer’s representative will want to sit down with you to review your utility bills. Then there’ll be a discussion of how much you can expect to save on monthly bills and a rough estimate of installation costs. The estimator will be knowledgeable about your local utility rate structure and net-metering regulations, and may suggest ways to reduce energy use and thus the size of the PV or SDWH system.

The estimator will want to climb out on the roof to gauge the amount of sun it gets and what kind of shade to expect as the sun moves across the sky, summer and winter. A critical issue is the condition of the roof itself. The solar array components carry a warranty of 20 years or more, and you probably don’t want to bolt it onto roofing tiles that will need to be replaced in five or ten years.

Ask about subcontractors. Is the installer going to bring in a licensed electrician or roofer? If so, who is responsible for the quality of their work? Who, for instance, will be responsible for roof leaks?

Ask about leasing programs and financial terms, of course. The estimator will have a good grasp of local incentives and grant programs, and should be able to reel off a list of banks offering “green” loans for home energy projects (banks and leasing companies often have their own lists of approved components and installers). The estimator should also explain the tax implications of local incentives and how they affect your federal tax credit.

Once the estimates are in, compare them carefully. Make sure that all the bases are covered: Are the estimates all for the same size system? Are there performance warranties? Who handles the permitting and inspection fees, and are all applicable taxes accounted for? What are the warranty and service-visit policies? What about cost overruns – if fees or charges rise unexpectedly, who pays?

Scheduling and installation

Once you’ve settled on an installer, negotiate firm dates for installation and commissioning (that’s when the completed system has been inspected and is actually connected to grid and running). A post-commissioning visit from the installer should validate system performance, and the rep can explain the inverter’s monitor display so you can track power production. Be sure to get the equipment manuals and warranties and file them safely.

Figuring the financial value of a solar or wind energy system.

By Andy Black

How long will it take for a new solar or wind electric system to pay for itself? That depends on your local climate, utility rates and incentives. In sunny or windy states with expensive electricity, the payback is faster than in calm or cloudy states or where power is relatively cheap.

In some regions, solar systems are allowed to operate on a time-of-use rate schedule, enabling users to sell back electricity to the utility at peak rates, which can be even more valuable. Time-of-use rates vary in price by time of day (see charts below), with higher rates during times of power shortage (for instance, when air-conditioning loads are high). That’s when the utility must pay more to purchase electricity from generators. These higher electric rate periods often occur in the heat of the day, when solar systems are most productive.

It seems that everyone is interested in wind turbines, an intriguing technology that converts the kinetic energy in the moving wind to useful electricity. Let’s look at the steps required to see if a small wind system (defined as up to 100 kilowatts in nameplate capacity) is in your future.

Step 1: Examine why you want a wind system. Energy independence?  Lock in future energy costs? Return on investment? Do your part to mitigate global climate change?  Support the renewables industry? Power an electric vehicle? Set an example for your family and community? Put your money where your values are?

These are valid reasons for installing a wind turbine. Your goals will affect the system you choose, the amount of money you are willing to spend, and the time you are willing to commit to being your own utility.

Step 2: Quantify the amount of electricity you use now. Most people put up only one wind turbine and they usually want it to generate the amount of electricity they consume over the course of a year. Cost-effectiveness changes with increasing size — the bigger the turbine, the more you spend on the installation, but the cheaper the cost of electricity will be over the life of the system. Matching the size of the system to your annual load maximizes the value of your investment if you can’t sell the excess.

Step 3: Re-evaluate how you use electricity and why. It’s always cheaper to save energy than it is to generate it, so streamline your consumption. The most cost-effective way is to alter your electricity-use habits — turn off lights in unoccupied rooms, mind the thermostat, put “vampire” electronics on a switchable power strip.  But habits are hard to change. Investing in high-efficiency appliances makes excellent sense. The rule of thumb is that every $1 spent on efficiency saves $3 in wind system costs.

Step 4: Determine how much fuel (wind) you have at your site. The best way is to hire a small-wind site assessor to evaluate your site and wind resource. This service may be available for a fee from a local wind installer, but be sure to shop around. You want an assessment of your wind resource, not a sales pitch for a particular turbine or manufacturer.  Consider this akin to hiring a building inspector to evaluate a house you are interested in buying. The inspector’s job is to evaluate the condition of the house and report back to you so you can make an informed decision as to whether or not the house is a wise investment.  During this process, the inspector represents your interests only, as should a wind site assessor, and present you with unbiased information to evaluate.

Step 5:  Determine the minimum acceptable tower height for your site. The rule of thumb for sizing a tower is that the entire rotor of the wind turbine must be at least 30 feet (10 meters) above any obstacles within 500 feet (150 meters) of the tower, or above the prevailing tree line in the area, whichever is higher. In most cases, trees will be the major obstacles that you need to clear.  Keep in mind that you will have the system for 20 to 30 years, so you will need to estimate the mature height of the trees in your area, not their current height. While short-tower installations are rationalized as a way to save money on the system, the electricity generated is invariably a disappointment compared to the incremental cost of a taller tower. In addition, short towers mean that the turbine will be affected by turbulence. That not only reduces power production, it causes undue wear and tear on the equipment, compromises reliability, and shortens the turbine’s life.

Step 6: Determine the best location on your property to site the tower, based on elevation above surrounding obstacles and prevailing wind direction. For best access to winds, the tower needs to be upwind, as much as possible, of the buildings and trees in the area.  Other considerations include access to the site by excavating equipment, cement truck and crane. Putting the system close to the house may minimize the length of the wire run and save money, but if the close-in site compromises the turbine’s access to good, clean laminar winds, you’ll pay for it later in reduced power.

Step 7: Research turbine options from reputable companies with a history. Be cautious about being the first person to buy a new turbine model or equipment from a new manufacturer. You want tried and proven equipment, not a “technology breakthrough” with no track record of performance and reliability. Check with the Small Wind Certification Council for turbines certified to the American Wind Energy Association (AWEA) Small Wind Performance and Safety Standard, or which have begun the process of certification.

Step 8:  When shopping, look for the turbine’s annual energy output (kilowatt-hours per year) at your average annual wind speed at tower height for your site. The “power rating” in watts is meaningless, because it’s stated for some specific wind speed you may rarely see at your site. Power rating says nothing about how much electricity you will generate, or how long the turbine will last.

Wind power is collected and converted by the rotor, so the single most important characteristic of the turbine is its rotor size. A wind turbine with a small rotor can only generate small amounts of electricity. It won’t power your entire house or farm.

Step 9: Shop for what you need, not based on cost. You need a turbine that will last for decades, generating electricity quietly and reliably. Shopping based on cost can result in the most expensive electricity you can buy, because it invariably leads you to an unproven turbine, an inexperienced manufacturer, a small rotor mated to a large generator power ratings, or a short tower.

Step 10:  Look for an installer with a good reputation, who has been in business for a while. Ask for referrals, including references from the turbine manufacturer the installer represents. Make sure to ask for several customers whose sites you can visit. A wind system is a major purchase. You want a qualified, experienced and dedicated installation company who is in small wind for the long haul.

Step 11:  Finally, remember that small wind turbines having moving parts that interact with all that nature throws our way. Any wind turbine needs periodic inspections and maintenance, and eventual repairs. This is where the installer and the turbine reliability become really important. A competent installer and quality equipment will give you decades of reliable service and electricity. If you cut costs on either, you’ll likely end up with a short-lived system.

———-

Mick Sagrillo, of Sagrillo Power & Light is a small-wind consultant and educator. Contact him at msagrillo@wizunwired.net. Illustration by Kurt Struve. Graphic courtesy of Dan Chiras.

Copyright Kurt Struve

Ground-source heat-pump (GSHP) heating and cooling, often called a geo-exchange or geothermal system, is an efficient way to keep a house comfortable. The Environmental Protection Agency says a GSHP system can save 50 to 60 percent on a typical home heating bill. About 1 million GSHP systems are currently in use in the United States, and about 50,000 new systems are installed annually.

How It Works

A heat pump works like a refrigerator: It uses a fluid and a compressor to move heat from one side of a wall to the other. A refrigerator chills the air inside by warming the air outside; an air-exchange heat pump does the opposite, warming the air inside the house by cooling the air outside. Think of it as an air conditioner turned backward.

A ground-source heat pump does the same thing, but it works off the stable temperature of the soil or groundwater under your property. Depending on your geology and climate, the soil beneath your house and yard remains at a remarkably stable temperature year-round — in most parts of the country, that’s within a few degrees of 55°F (12°C). A network of pipes buried in the soil can function as a heat exchanger, keeping its working fluid at ground temperature (the heat-transfer fluid can be water, water mixed with antifreeze, or a refrigerant). The heat-pump compressor uses the transferred heat to warm the inside of the house without directly burning fuel.

Components

A small house typically requires about 3 tons of heating/cooling capacity, equivalent to about 10.5 kilowatts. A system of this size might use about 1,500 feet (about 450 meters) of tubing buried in loops near the house (the length of the tube will vary with climate). An electric pump sends the working fluid through this loop field. A heat pump replaces the original furnace or boiler. This unit transfers heat from the loop field to the inside of the house.

Most systems use polyethylene tubing as the buried loop field and pump water through it. Modern “direct exchange,” or DX, systems use a loop field of copper tubing filled with a refrigerant. This arrangement is more expensive to purchase because of the cost of the copper and refrigerant, but the system may be less expensive to install because the buried loop is shorter. It’s also less expensive to operate because the refrigerant-to-earth heat exchange is more efficient than interposing a water-to-refrigerant heat exchanger.

The heat pump inside the house can come in two flavors: water-to-air and water-to-water. A water-to-air pump heats air for a forced-air heating duct system. A water-to-water pump heats water for circulation through a hot-water or radiant-floor heating system. A hybrid system heats both air and water — you could have both forced air and radiant heat or use the hot-water output to augment the domestic hot water supply.

Cost, Payback

The U.S. Department of Energy estimates that a GSHP system costs about $2,500 per ton of capacity, or roughly $7,500 for a 3-ton unit. Energy savings may provide payback in about five years. For installation considerations, see the Department of Energy website. Visit the Energy Star website for ratings of ground-source heat pumps.

———-

It’s cheaper to save energy than to make energy. If you want to offset $100 a month in utility bills, the right place to start is not with a solar array on the roof, but with insulation under it.

First, look at your heating bills.

If you heat with natural gas or fuel oil, it’s easy to find the separate monthly item even if it’s billed by your electric utility. If you live in the wintry northeast and burn heating oil, it’s easy to pay $1 per square foot annually to heat a house. That often adds up to more than $2,000 a year. Most homeowners can save 20 to 25 percent by caulking air leaks around windows, doors, foundations and soffits.  Check the attic insulation, too. It’s cheap to add an extra layer of batting or blown-in cellulose. It’s more expensive to swap out old single-pane or metal-frame windows for more efficient modern insulated triple-pane wood- or vinyl-frame windows. The cheapest fix of all is to renew weather-stripping around all doors and window sashes, and put insulating covers on pet doors.

Spending $2,000 on insulating upgrades may cut heating costs by 50 percent and pay for itself in about three years. The Department of Energy website includes interactive worksheets to help you figure out how much more insulation you may need (depending on your climate), how much it may cost and, depending on what you’re paying for heat energy today, how long the payback period may be.

Heating and cooling systems can usually be improved. Be sure to change the furnace air filter quarterly. Get ductwork cleaned and air leaks sealed, and make sure that ducts are insulated at least to local codes. Your ductwork should be set up to heat (or cool) re-circulated air from inside the house, but the furnace should draw combustion air from outside — you don’t want to burn fuel using air you’ve already paid to heat.

If you heat with oil or electricity, consider installing a modern high-efficiency gas furnace or ground-source heat pump. A $6,000 investment in insulating and HVAC improvements might pay for itself in five or six years.

Not sure where to start? The most direct way to find cost-effective fixes, especially in an older house, is with a professional energy audit. Check with your utility company to see if they offer free or reduced-cost audits. Standard price for this service is $200 to $400. It may include a blower-door test to locate air leaks.

Look into energy-efficient appliances.

The typical refrigerator built in 1980 costs about $154 in electricity to run for a year, at today’s average rate of 11 cents per kilowatt-hour. A modern high-efficiency refrigerator runs for about $55 a year. The average homeowner would save $99 a year ― enough to pay for the refrigerator in a few years. A modern front-loading clothes washer uses far less hot water than the old top-loaders, and that saves money.

A new water-heating system may be cheaper still. A simple warm-weather solar water-heating system may cost less than $2,500 to install, especially if you do it at the same time you replace your electric hot-water heater. Depending on where you live, it may cut your water heating costs by 40 to 50 percent. A large family with lots of kids uses plenty of hot water for bathing, laundry and dishwashing, so this can be a significant power saving. Read more about solar water heating.

Most hot water heaters can be made more efficient. Fix all leaks. Turn the thermostat down to 122°F (50°C). Be sure all water lines, and the tank itself, are fully insulated. Use low-flow shower heads.

The Department of Energy publishes a list of high-efficiency appliances on its Energy Star website.

Most people already know that the easiest way to cut your electric bill is by replacing incandescent light bulbs. Incandescent bulbs waste about 95 percent of their energy as heat. If you run six lamps for six hours each night, (let’s say one light each in the kitchen, dining room, living room, bedroom, bathroom and hall), using 15-watt long-life compact fluorescent lamps (CFLs) would save $72 in the first year over incandescent bulbs.

Does someone in the house leave the color TV set on for hours at a time?  With its cable box, it burns about 310 watts. TV sets (and computers too) can draw 5 to 10 watts continually, even when shut down, unless you pull the plug. Solution: Use a switchable power strip. A large attic fan may draw 370 watts, but that’s cheaper than an air conditioner, which draws about 1,900 watts per ton of cooling capacity.

Edited by Barry Butler, Liz Merry and Diana Young

In most parts of North America, the best bang for your solar energy buck is with domestic solar water heating (DSWH). It’s a no-brainer in the desert Southwest and in semitropical Florida and Hawaii.

A complete DSWH system can be installed for $4,000 to $7,000, depending on its size, complexity and the climate. These systems are now eligible for the 30 percent federal tax credit. At today’s energy prices, over the life of the system, the cost to operate is about 20 percent lower than a conventional gas water heater and 40 percent lower than an electric one. As gas and electricity prices rise, DSWH will look like a better and better deal. The benefits are much greater since solar energy avoids 2,400 pounds of CO2 per year and provides a secure domestic source of hot water.

Solar hot water systems come in two flavors: passive and active. In warm climates, a simple passive system can provide plenty of hot water.

Passive Solar Water-Heating Systems

Passive systems are installed in areas where freeze protection is not an issue. The most common types are integral collector storage (ICS) and thermosiphon systems.

In an ICS (or breadbox) system, cold city water flows into a rooftop collector. The collector holds 30 to 50 gallons of water in a serpentine pipe with a heat-capturing coating. Hot water from the collector flows directly to a conventional water heater; in effect the sun does most of the work usually performed by the water heater’s burner. As hot water is withdrawn from the water heater, cold water is drawn into the collector, driven by pressure in the city water pipes.

This system, installed by Star Max Solar, uses a flat-plate collector and a PV-powered pump.  Photo courtesy of Star Max Solar.

A thermosiphon takes advantage of the fact that water rises as it’s heated. Solar-heated water in a flat-plate collector rises through tubes and flows into the top of an insulated storage tank. Colder water at the bottom of this tank is drawn into the lower entry of the solar collector. Water thus flows in a continuous loop, continually reheating during daylight hours. When a hot water tap is opened in the house, hot water flows from the top of the storage tank, and is replaced with cold city water flowing into the bottom of the storage tank.

Although the system is simple, thermosiphons put an 800-lb storage tank high on the roof, which should be reinforced to support it. Other solar water-heating systems put the storage tank at ground level or in the basement, where it’s not a structural challenge.

Active Solar Water-Heating Systems

Active systems use an electric pump to circulate water through the collector. In warm climates, a direct (or open-loop) system is practical: City water goes into an insulated storage tank. A pump draws water out of the storage tank to pass through the solar collector and go back into the tank. Hot water for household use is drawn from the top of the storage tank, sometimes passing through a booster heater. An automatic control system starts the pump whenever the collector is warmer than the storage tank.

In freezing climates, the rooftop part of the system must be protected either by draining down when the temperature dips, or by running an antifreeze solution. These cold-weather systems require temperature sensors, electric pumps and automatic control systems, adding complexity and cost to the installation.

The most common cold-weather system today is the closed-loop antifreeze heat-exchanger system, or active indirect system. When the collector is warm, a food-safe propylene glycol antifreeze solution is pumped through the collector and on through a heat exchanger, then back to the collector. The heat exchanger heats city water for domestic use. The heat exchanger is usually located at the bottom of an insulated storage tank (sometimes the storage tank is also the home hot-water heater, with an electric or natural gas heating mechanism for use when the collector is cold). A breach in the heat exchanger would leak antifreeze into the drinking water, which is why it’s necessary to use only food-safe propylene glycol in these systems. Many local plumbing code officials require double-walled heat exchangers to permit systems in their jurisdictions.

Swimming Pools and Hot Tubs

One of the most common uses for solar water-heating is to heat pool water. Pool solar collectors are lighter in weight — usually made of UV-resistant polymers — and less expensive than DSWH systems. The size should be 50 to 100 percent of the surface area of the pool. The more solar collector area, the warmer the pool will be in cool weather. The pool serves as the storage tank, and the filtration pump circulates the pool water through the collectors. A solar collector can provide all the heating necessary for a swimming pool, but hot tubs and spas need a backup or booster heater.

Space Heating

DSWH can also be used for space heating. The most efficient method is an in-floor radiant heating system that sends hot water through pipes embedded in the floor. Agas backup water heater is typically used because a house is coldest at night and in winter months. The solar collector area needed is generally 10 to 30 percent of the home’s floor area, depending on climate.

Maintenance

All hot water heaters and solar system storage tanks need to be flushed annually. The pumps and valves in an active system are electro-mechanical devices that will need periodic attention. Annual pressure testing can identify potential problems before they become major leaks. Long-term corrosion is an issue in any plumbing system, but a well-maintained system can go 35 years or more before replacement of major parts.
———-

This article is adapted from the Solar Energy Resource Guide 2008, published by the NorCal Solar Energy Association, a chapter of the American Solar Energy Society.

Illustration by Kurt Struve.