The design of every new building at the monastery includes consideration of the solar energy systems that will be used. Designing the building and solar systems together not only saves money, it enables the two to work together and perform at a level not always obtainable with retrofit systems. Better performance means reduced fuel costs and consequently, lower greenhouse gas emissions. The hot water system shown here provides the bulk of the energy for domestic hot water and space heat in a building that houses 20 monks.
The solar water heating system is made up of components which can be grouped into the following subsystems:
Each of these subsystems is discussed in detail below.
The solar water heating system is made up of components which can be grouped into the following subsystems:
- Heat Collection
- Heat Storage
- Heat Distribution
Each of these subsystems is discussed in detail below.
Heat Collection
The sun's energy is captured by Solar Collectors, which are mounted on a south-facing roof and tilted up to face the sun. Here we used fifteen collectors, arranged in three banks of five. The collectors are insulated boxes with black copper tubes running through them. Whenever the sun is out (as determined by a small computer, believe it or not), a pump is activated to circulate water through the collectors. The water picks up heat to be used later by the system. Toward evening as the sun's heat diminishes, the computer signals the pump to stop work for the day.
Heat Storage
The water that circulates through the collectors eventually comes to rest in a 1000-gallon storage tank. The tank is heavily insulated, since the heat may not be needed until much later, after nighttime cold sets in. Although the water may circulate through the collectors for just five hours of a winter day, the tank temperature can reach 150° F! In summer the tank could get much hotter, but the computer shuts off the pump at about 170° F to prevent overheating.
Heat Distribution
The heat in the storage tank is utilized for both domestic hot water and space heating. For domestic water, the cold incoming water is preheated by passing it through a coil in the storage tank before it goes to the domestic hot water tank. This reduces the fuel required to heat the water to its final temperature. Space heat is accomplished in similar fashion using another coil inside the storage tank. The building has tubes in the floor through which hot water is circulated to heat the rooms. This water is heated by passing it through a coil in the (hot) storage tank. If the tank runs short of stored heat, a backup boiler handles the balance of the job.