Renewable Energy Sources

There are a number of renewable energy sources. These include solar, wind, biomass and tidal power. Of these, only solar is appropriate for buildings (homes, businesses, institutions). Solar power comes in two forms: photovoltaic panels which convert sunlight into electricity, and glass or other material collectors that heat water to supplement hot water heaters. Solar hot water heaters, in particular, have an excellent return on investment (ROI).

Photovoltaics have an energy payback time of 1 to 3 years, depending on available sunshine, and newer technologies are moving away from silicon-based systems to photovoltaics that are plastic and can be applied to almost any type of surface, such as roof tiles. The newest of these can be applied in flexible strips up to four feet wide and as long as 500 feet. Photovoltaic-generated electricity can be stored in batteries for use when there is no sunlight or the electricity can be placed in the electrical grid (your meter actually runs backwards). Current law requires electricity utilities to purchase your electricity at the same rate they charge you (net metering).

A solar hot water heater can reduce residential or commercial hot water heating by about two-thirds. Solar hot water systems are either active or passive, with active systems the most common. Active systems use pumps and controllers to circulate water or other heat transfer fluid through the solar collectors. Passive solar hot water heaters use gravity and the thermal gradients to circulate water through the system. There are no electrical parts and are generally easier to maintain. The energy payback time is a function of hot water usage and is particularly short for solar water heaters used for swimming pools, typically 1-2 years.