Block’s Indicator of Sustainable Growth

by Ray Block

 The International Energy Agency conducted a three year research program between January 1 2005 and January 1 2008 on the marketing and commercialising of PV/Thermal systems that combine the production of electricity and heat in the one unit.

The Danish Energy Authority acted as the coordinator of the research efforts. As a result, a number of innovative companies have developed PV/T integrated systems, combining solar photovoltaic cells with a solar thermal collector, forming the one device that converts solar radiation into electricity and heat simultaneously. Most systems combine the PV/T module with components- such as hot water tanks, heat exchangers, piping,

controllers, inverters, wiring and heat pumps.

“Because of their high efficiency per unit surface areas, PV/T is particularly well suited for applications with both heat and power demand, and with limited roof space available. Therefore, the potential of PV/T is especially large in the residential market.”

The IEA deserve great praise for their efforts. “PV/Thermal modules can generate more energy per unit surface, than side by side photovoltaic panels and solar thermal collectors, at a potentially lower production and installation cost. Moreover, PV/T modules share the aesthetic advantage of PV. Because of their efficiency per unit surface area, PV/T is particularly well suited for applications with both heat and power demand and with limited roof space available.”

The most promising applications for PV/Thermal systems are water heating and space heating. The Danish Energy Authority says that to ensure a successful implementation of PV/T as desirable market products, it is “essential to agree on performance and reliability standards for PV/T, and to increase the optical and thermal efficiency, and the long term reliability of PV/T, with the ability to be fully integrated in the building shell.”

There are many ways to combine the different PV and Solar Thermal technologies to a PV/T collector. For example, do you use the European or Japanese crystalline silicon PV panels. Or the American thin film PV panels. For the collector, do you use a liquid or air collector, flat- plate or concentrating technologies, with or without transparent cover.

Most development has been done with silicon panels and liquid and air, flat-plate type collectors. The researchers have also been using concentrating and combined liquid/air PV/T collectors. The busy Danes conducted market research and field surveys relating to solar dealers in the US, Canada, Germany, Italy, Spain and Sweden. Architects were also interviewed. “Almost all respondents are very positive to PV/T and see different advantages.”