Reducing Our Environmental Footprint - Sun Power at the Wedge

The renewable energy of the sun and the technology that supports its use are important resources for reducing our reliance on the earth's finite supply of fossil fuels.

During the past 100 years, human beings have consumed nearly half of all the oil derived from the earth's fossils that will ever be produced. As a local business in a northern climate, our challenge is to reduce reliance on costly fuel systems and maximize use of solar power.

One solution to this challenge is a solar hot water heating system recently installed at the Wedge by Innovative Power Systems, Inc., a Twin Cities renewable energy provider. On the roof of the Wedge Co-op's new bakery addition is the most visible part of this system - a 30 foot-long array of solar collectors. The system preheats the cold water supply from the city before it enters our (conventional) gas-fired hot water heater. This step reduces the amount of natural gas which the Co-op must purchase to heat water.

The solar array consists of seven 4' wide by 8' tall flat-plate collectors. Each collector is a weather tight box, housing copper tubes with copperfoil "wings" covered with a black coating, which absorbs heat from the sun. An antifreeze solution (75% propylene glycol and 25% water) is circulated through the copper tubes, absorbs the heat, and carries it to the solar storage tank where it heats the Wedge's water supply. In contrast to "passive" solar systems, in which there are no moving parts, this is an "active" solar system: a pump is used to circulate the fluid through the system.

The Wedge is a busy store with an almost continuous need for hot water during the day, and the solar heat is used as fast as it is collected. This allows for greater efficiency of the system, with very little storage loss of heat. We expect that the solar preheat system will typically raise the temperature of the incoming water about 25 degrees F. So, if the cold water comes in at 50 degrees F, and the solar heats it up to 75 degrees F, then the gas heater only has to heat the water from 75 degrees up to the desired hot water temperature of 120 degrees. Thus, only about two-thirds as much natural gas is required for heating the water.

Ralph Jacobson, owner of IPS, makes the point that solar heating should be viewed as a "natural ally" (all puns intended!) of natural gas, and not as a competing technology. "Gas is a very convenient way to heat water and buildings, causing less environmental damage than other fossil fuels. We also know that we will run out of it sooner or later - it's not a question of 'if,' but 'when.' Solar heating can help us stretch the natural gas resource, using gas only to fill in at those times when sunshine is not available or can't do the whole job. And this solar water heating system at the Wedge is a perfect example of the two energy sources working together to keep the co-op in hot water!"

Reducing the amount of fossil fuel used and eliminating emissions into the environment are two ways the lower cost of solar energy is realized. This is one step in our long term commitment to reducing our environmental footprint at the Wedge. Installing solar panels is another way the Wedge Co-op "walks the walk."

Innovative Power Systems installs and does maintenance for businesses and homes in the Metro area, with regional sales in Wisconsin and the Dakotas. Their office is located at 1153 16th Ave. SE, Minneapolis. Their phone number is 612-623-3246 or visit them on the web at www.IPS-solar.com