Solar power effective method for space heating

Dear Jim: The sun feels warm shining in a large south-facing kitchen window. I don’t have a lot of money to spend, but I would like to find a simple method to get more of the sun’s heat. What are my options? -Stephen G.

Dear Stephen: There are many simple methods to use the sun’s energy to heat your home. Solar energy is effective for space heating (room air) in all climates. It is particularly effective in mild climates where the heat loss back outdoors through windows or a heater is less than in colder climates.

Your large kitchen window is one of the best passive solar methods to heat a home. A southern exposure is best for solar heating because the sun’s rays are most intense from noon to early afternoon when they are from the south.

The key to maximizing the total solar heat gain is to use thermal mass to store the heat. When the sun no longer shines into the room, the thermal mass will slowly transfer its stored heat into the room air as it cools. Without thermal mass, the room will overheat when the sun is shining, lose more heat back out the window and cool down quickly.

Masonry has a high thermal mass. A low-cost method is to paint some concrete blocks black and use them to support planters, a bench, etc.

When the sun shines on them, they will absorb the heat. A terrarium with a lot of soil and sun-loving plants is also effective thermal mass. A dark container filled with water is the most effective method for storing the solar heat.

If you are a handyman, build a Trombe wall close to the kitchen window. This is often made of stacked bricks (remove during summer) to partially cover the window and add a clear acrylic sheet above it. It is designed with vent gaps near the bottom and a gap at the top. When the sun shines on the bricks, it creates a natural warm air current as it also stores the heat for nighttime.

Several designs of simple solar heaters can also be built for about $100 in materials or less if you have some scrap lumber and an old storm window or door. The simplest design is a shallow, flat box which is mounted vertically outdoors on the southern wall. Install short pieces of metal duct through the wall at the top and the bottom to connect it to the room.

Paint the inside of the box flat black. Use an old storm door or acrylic sheet over the open side of the box which faces the sun. As the box heats up, the warm air naturally circulates up and out into your kitchen. You can add some black metal mesh or expanded metal inside the box to increase the solar heat gain. Remember to seal off the duct openings each night.

Another option is to tilt the box at an angle from the house so the clear top faces the sun more directly. Your local weather service can advise you about the proper angle for your area of the country. With this design, you must insulate the box and short ducts. During the summer, close the top indoor vent and open a top outdoor vent to naturally ventilate and cool your kitchen.

Dear Jim: I need to replace my water heater. I have been looking for a microwave-powered, tank-type water heater. I imagine it would be much more efficient than a standard water heater, but I cannot find one? – Pete S.

Dear Pete: Actually, a microwave-powered electric water heater would be less efficient than a standard water heater. With a standard one, nearly all of the electricity used goes into heating the water in the tank.

When you select your water heater, look for one with the highest insulation level. The efficiency of a water heater is rated by its EF (energy factor). Ones with the thickest insulation often have the highest EF.

Send inquiries to James Dulley, Bangor Daily News, 6906 Royalgreen Drive,

Cincinnati, OH 45244, or visit www.dulley.com.