SOLAR TODAY - March 2009

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renewable energy stuff
Ener Works Earns
Energy Star Rating for Solar
Water-Heating Systems

Ener Works solar water-heating appliances are the first to qualify for the Department of Energy’s new Energy Star residential water heater program. Ener Works’ two-, three- and four-collector solar water-heating systems, as well as all SpaceSaver single-tank solar and electric appliances, now bear the Energy Star registered trademark. The Energy Star program for residential water heaters went into effect Jan. 1. Qualifying products are posted on the energystar.gov website. See qualifying solar water heaters at tinyurl.com/ energystar-solar water.

enerworks.com

PC Controls
Residential-Scale Heliostat

Practical Solar Inc. of Boston has introduced the world’s first PC-controlled, hand-installable heliostat system. The computerized mirrors reflect sunlight onto a fixed target and can be used for anything that requires light or thermal energy. On a clear day, a single heliostat provides as much visible light as 40 100-watt light bulbs, as well as 600 watts of thermal energy — equivalent to a space heater on a medium setting.

The heliostats can provide natural lighting and direct space heating to areas that do not ordinarily receive direct sunlight, like the north-facing rooms of houses or buildings. The system can also be used for concentrating solar power (CSP). Used with an ancillary product like a CSP receiver, the heliostats can be used for building heating and cooling, desalination, low-temperature industrial processes and electricity generation.

The system tracks the sun, controlled by a standard personal computer. The company provides software and a driver box that can

control up to 200 heliostats. The control software runs in the background so the computer can be used normally.

Each heliostat can have any number of targets. Switching between targets takes only a click or can occur automatically with the software’s built-in timer function. For example, a single heliostat could automatically provide natural light and heat to an upstairs bedroom in the morning, to the kitchen at lunchtime and to the home office in the afternoon, without any prompting from the user. A user with two heliostats can focus all 1,200 watts of thermal energy onto one target or have the heliostats reflect sunlight to different targets. Programming a new target takes only a few minutes.

Practical Solar’s two-axis tracking technology is math- and software-based, so the system avoids the reliability pitfalls of sensor-based sun trackers. Heliostats are designed for easy shipping, and can be installed with hand tools.