Solar-heated water already shows energy savings
Posted on Wednesday, August 22, 2007
The new solar water heater at Fire Station No. 7 will help make the case for renewable energy at the state level, as well as provide hot water for the station and help the city save money in energy costs.
“ This is an investment that will save money over time. Now is the time and it’s not going to be that much time, ” said William “ Bill ” Ball of Little Rock, chairman of the Arkansas Renewable Energy Association, in a meeting at the station Tuesday to explain the design and installation of the solar water heating system.
As described by Ball, the city is using less energy to heat water at the fire station because the water going into the regular water heater has been preheated by the sun.
The city of Fayetteville received a $ 10, 700 grant from the Arkansas Energy Office for installation of the solar water heating unit.
“ The city did it because we’re trying to conserve energy, ” said Coy Hurd, building services director for the city. “ Because this was a grant to us, we could build the system for no cost to the taxpayers, save some energy and save some money. ”
The system was originally planned for Fire Station No. 4, but there was not enough room at that station.
Ball said the city saved 107 kilowatt hours of energy in a little more than a week. When all the measuring devices are installed, the system will monitor the natural gas used by the water heater, the flow rate and temperature of water into the tank, and the temperature of the water leaving the tank to determine kilowatt hours saved.
It’s a tale of two tanks: one that holds water heated by solar power and the conventional water heater tank that gets preheated water from the solar tank.
Ball said a heat-exchange fluid carries the sun’s heat from the rooftop to a tank in the fire station. The hot fluid in a coiled copper tubing radiates warmth to water in the solar tank. From there the warmed water is carried by pipes to the same water heater that was installed in the fire station when it opened, and the heatexchange fluid recirculates to the roof to be heated again.
“ The tank itself is a storage tank that stores solar-heated water and then provides that preheated water to the conventional tank that is still in position, ” Ball said. “ We did not take out the existing tank or anything. We’re using the gas-fired water heater that was already there before, except now it is receiving water that is already hot. ”
When firefighters turn on hot-water taps, they get their water at the same temperature and pressure from the same tank they always did.
“ Using renewable energy here has not had any effect on our quality of life or what we’re accustomed to as far as energy. There’s plenty of hot water, as a matter of fact, probably more, ” said Steve Cattaneo, building safety director for the city.
The difference is the water is already warm or hot when it goes into the water heater.
By day’s end, in the summer, the water in the solar storage tank can reach 160 degrees or higher. When the water is hotter, a tempering valve lowers it to 160 degrees before it is transferred to the conventional tank.
In winter, the sun-warmed water may only reach 100 degrees, but that is still far higher than cold water from outside and means less electric or gas energy is needed to heat it, Ball explained.
“ We should hit well over half, maybe approaching 70 percent, of the hot-water load (at the fire station ), ” he said.
The solar tank is not hooked to electric or gas power.
“ It’s just sitting there storing hot water, ” Ball said.
The two solar electrical panels on the roof make electricity that runs the circulating pump carrying the heated fluid to the solar storage tank.
The existing or conventional tank doesn’t have to use power to heat the water at all, nor does it have to use as much power to heat the already warm water to 160 degrees.
“ Even in December, (the conventional water heater ) has to work much less hard to maintain that temperature, ” Ball said.
Cold water is piped into the building as it always has been, but it’s diverted to the solar tank before it goes to the main heater.
“ The solar’s going to work on it, ” Ball said. “ Depending on the time of year, it’s going to raise it 20, 30, 40, 50, 60 degrees or 100 or 110 degrees. ”
Besides providing hot water for less money at Station No. 7, it’s Balls’ hope that this installation, along with others like it in public places in Arkansas, will prove that using solar hot water is cost-effective.
“ If we can make an argument for ratepayers supporting more insulation in attics because it’s cost-effective, we can also make an argument for ratepayers supporting solar-power hot water systems because they’re costeffective, ” he said.
In about a year’s time, Ball will take the reports of the energy savings from this and other Arkansas sites to the Public Service Commission to make the case that renewable energy like solar water heaters should be identified as energy efficient.
The hope is to create what are sometimes called clean energy funds collected as part of utility bills and can be directed to help lowerincome individuals and families with energy savings.
“ Just a few dollars spent in the right area can make a tremendous difference in utility usage, ” Ball said. “ That’s why we were able to get the state grant to put the solar hot water heater on the station, so we could raise the awareness of solar hot water and the fact that it has a wonderful cost return. ”
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