James and Tomi Allison recently had a solar water heater installed on the rear roof of their Elm Heights home.

“We’ve been interested in reducing our consumption of fossil fuel for some time,” James explained. Mindful of their carbon footprint, he and Tomi drive a Prius hybrid car and have reinsulated their home for energy savings.


“Our interest began back in the ‘70s when the gas crisis hit,” James noted. “Back then there was a lot of interest in solar panels.” Recently the couple began to look again at solar options but found it difficult to locate anyone who had sufficient expertise in this technology.

“I told a friend of mine that I had searched the Bloomington and Indianapolis phone books and hadn’t found anyone, and she gave me some names,” he said. “The one who seemed most capable was Alex Jarvis of Solar Systems of Indiana.”

Alex, whose solar installation on a home at South Dunn Street was recently featured in “Homestyle,” performed a solar assessment at the Allisons’ home to determine how many hours of sunlight their roof received throughout the day. The roof on the rear addition of the home offered abundant sunshine.

“It seemed to us that the best thing to start with would be this solar hot water system, which is one of the oldest and most developed technologies,” James continued.  Six months after the Allisons contacted him, their new solar water system was in place.

So how does a solar hot water heater work? There are several components, the most obvious being the large flat box now attached to the roof behind the house.

“It’s carefully engineered, very efficient,” pointed out James. “On a day when the ambient temperature outside is 80 or 90, it’s 140 degrees inside. In the winter it does the same thing. All you need is sun.”

He pointed to white pipes that lead from the box on the roof down to the basement.

“It circulates antifreeze – a polyethelene glycol mixture,” he continued. “It’s pumped up from the basement through an insulated pipe and winds up in the upper corner of the box. It flows downward through a system of fins, absorbing the sun’s heat as it goes. It reaches the bottom corner by gravity feed and then drains back into the basement.”

How does the system know when to pump?

“There’s a temperature sensor up on the roof, and another sensor in the basement. When it’s 11 or 12 degrees different, and warmer on the roof, it automatically begins to pump the glycol mixture up. At night it doesn’t pump because it’s warmer in the basement than on the roof.”

The solar hot water system works in tandem with the Allisons’ old electric water heater. Whenever the sun shines, the warm antifreeze drains from the rooftop into the heat exchanger in the basement, which passes the heat into water in a storage tank, which then passes into the water heater. At night or when it’s cloudy, the electric water heater continues to function.

“According to the calculations, on a sunny day this system will generate the equivalent of seven kilowatt hours of electricity if it works for five hours,” James explained. “These pumps use 1.25 kilowatt hours, but the net energy gain is positive.”

Is Indiana sunny enough for a solar system to work? Absolutely, according to James.

“On the average you’ll have about 185 sunny days here each year,” he said. “If you do the math you’ll come up with about 1100 kilowatt hours for the year. Past experience suggests that’s about 12% of our yearly energy use. That means we’ll be reducing our power bought from Duke Energy by about 12%. The amount of money saved will depend on Duke’s current rate per kilowatt hour.”

Some readers might find a solar water heater, at several thousand dollars, a pricey way to shave a few hundred dollars each year off the electric bill. But James and Tomi don’t view it in those terms.

“I can’t control what Duke Energy charges, but I CAN control how many kilowatt hours I use,” James said firmly. “My motivation wasn’t just economic, but ecological. Whatever the power company might do, I will still have reduced my carbon footprint by 1.1 tons per year, including carbon dioxide, sulfur, mercury and heavy metals generated by burning coal. Even if it cost me money, I’d still do it. But it’s costing me LESS money.”

Since the system is still a new one, James checks each day to make sure it is operating according to expectations. So far, so good.

“I spend a little more on electricity to pump the antifreeze, but I spend less electricity on heating hot water,” he said.

James has a device called a “Kill-a-watt,” available on the Internet, which is essentially a miniature electric meter that plugs into the wall socket to measure how much electricity is being used by the pump. With it, he can also check the watts used by any household appliance or electronic device. Bear in mind that many stereos, TVs and electronic devices continue using electricity even when turned off. The Kill-a-watt makes it clear exactly how much juice continues to flow even when everything appears to be off.

“I encourage people to find out how much energy they actually use and how much they can reduce pollution,” James said. “A lot of people don’t realize how much pollution they’re pumping out. It amazed me that I could reduce my own pollution by 1.1 tons.”

He summed up, “People shouldn’t think about it just in terms of economics, but also about the environmental impact. If we all got together to do this, just think of the economic and environmental benefits!”

Reach Alex Jarvis of Solar Systems of Indiana at 336-2785 or www.solarsystemsofindiana.com.




Solar Domestic Hot Water

How it works, solar hot water systems for Midwestern climates:

On a sunny day, the solar collectors capture or collect the sun's energy. A pump circulates a food-grade antifreeze solution, polypropylene glycol and distilled water, through the collector array to absorb the solar energy. The heat from the solution is transferred to potable water in the solar storage tank via a heat exchanger. The solar storage tank is plumbed with the existing hot water tank so that when there is a call for hot water, the system is designed to pull hot water thru the existing hot water tank from the solar storage tank. A properly designed and sized solar hot water system will meet the majority (65-75%) of the household's hot water demands. The existing hot water tank will function as a back up and turn on only when there are extended days with no or little sunshine.

Drainback and Pressurized Closed Loop water heating methods explained

Drainback System is a solar water heating method where the solar fluid is pumped to the collectors and fills the solar loop piping when solar energy is available for harvest but drains back to a holding tank when not collecting energy. Drainback systems must be engineered properly so that they completely drainback to holding tank. Drainback are the simplest of all systems and should always be considered if there is a clear drainback path to the solar storage tank.

Pressurized Closed-Loop system is a water heating method where the solar fluid is constantly under pressure and are always in the solar collectors. They have no drainback holding tank as the system is always completely filled. With a glycol/water anti-freeze solar fluid, they can be used in cold climates and can have photovoltaic powered circulating pumps. They are “closed loop” so they require a heat exchanger in all applications. Because of the pressurized system, they can work where there is no clear cut drainback path.
Solar Hot Water System Costs:

General rule of thumb for system cost are $125-$175 per square foot of collector, depending on the relative difficulty of installation. A two panel system (64 square feet) would cost in the range of $8,000-$11,200 installed. Copper prices continue to rise and systems with long pipe runs are candidates to be on the higher end of cost range.

Example of System:
A two panel (4’ x 8’ collector) system, drain-back type, with a 50 gallon solar storage tank placed next to existing electric water heater. The existing tank would act as back up in periods of extended days of no solar energy.

System maintenance:

Solar hot water systems generally require little maintenance if installed properly. The system should be checked once a month to ensure it is working. The system should be observed on a sunny day to see that the pump is working and hot water is available. With pressurized systems, the solar fluid should be checked by a solar professional once every 10 years to make sure it has not degraded.

2008 Federal tax credit calculation: (for 2 system costs)
System cost low, $8,000 - $2,000 federal incentive = $6,000
System cost high, $11,200 - $2,000 federal incentive = $9,200
Average system cost after incentives: $7,600

Key Assumptions:

1) 1400 kWh/month of electric energy usage for residence; 16,800/year.
2) 15% of electric usage is for water heating.
3) 10% electrical energy offset from solar hot water heater per year on average, (.10 x 16,800 = 1680 kWh).
4) Average $7600 initial investment, ($9600 installed cost-$2000 federal tax credit = $7600).
5) 10% energy inflation.
6) $.10/kWh for first year electric energy cost per kilowatt/hour
7) 45,000 kWh offset over 30 year lifespan (30 yrs x 1500 kWh)
8) System maintenance over lifetime = increase in property value, 20 x 1st year energy savings (20x$168=$3360).
9) House or building has the structural strength and integrity to hold additional loads of a two panel system. (Check roof
joist size and spacing to determine).