As part of its plan to reduce its dependence on fossil fuels, the Kent County Regional Wastewater Treatment Facility in Milford, Del., in August launched a pilot program that is using 66 SPP-30A evacuated tube collectors to provide solar thermal energy for its biosolid drying process.

The resulting end product will be used by farmers to amend soil, by a local landfill as a daily cover or by a local cement kiln as a fuel supplement to coal.

The Solar Panels Plus collectors are part of a solar thermal radiant floor system designed to heat the concrete floor of three 240-by-80 foot-long greenhouses. The combination of the solar thermal heat and the passive solar capability of the greenhouses provides 40 percent to 50 percent of the heat needed to dry the biosolids. A natural gas-fired heating system provides supplemental heat when needed.

The challenge for the lead engineering company, Carew Associates Inc., was to generate the most heat possible in a very limited space, says Bob Cannon, president. The project was originally designed with flat plate collectors, but after comparing the BTU production capability of the SPP-30As to the flat plates the firm decided to go with the evacuated tubes.

"The main crux of the job dealt with saving energy and promoting green alternatives," he says. "We were looking for the most efficient means of using solar energy to produce solar heat."

The fact that the SPP-30A collectors were Buy American Act-compliant also factored into the decision. SPP assisted with laying out the 66 collectors in the available space and the project moved forward.

The project did not go unnoticed. Earlier this year, the Environmental Protection Agency Region III awarded its annual Pisces Award to KCRWT for its extensive environmentally friendly changes.

In addition to the solar-powered biosolids dryers, other innovative changes include a 1.2 megawatt photovoltaic solar farm and the switch from chlorine gas to an ultraviolet disinfection system.