Passive solar design refers to the use of the sun's energy for the heating and cooling of living spaces. In this approach, the building itself or some element of it takes advantage of natural energy characteristics in materials and air created by exposure to the sun. Passive systems are simple, have few moving parts, and require minimal maintenance and require no mechanical systems.
Your home's windows, walls, and floors can be designed to collect, store, and distribute solar energy in the form of heat in the winter and reject solar heat in the summer. This is called passive solar design or climatic design. Unlike active solar heating systems, passive solar design doesn't involve the use of mechanical and electrical devices, such as pumps, fans, or electrical controls to move the solar heat.
SOLAR THERMAL
Solar Thermal TubingSolar thermal systems are a cousin of solar electric systems. Rather than converting sunlight into electricity, solar thermal systems capture sunlight to make use of its heat energy.
Solar Thermal systems may be broadly split into three categories: (1) Water heating, (2) swimming pool heating, and (3) space heating (or cooling). Each utilizes variations on one simple technology: heating a thermal storage medium with solar energy. This storage medium may be used directly, as is the case with open-loop water heating, or indirectly, as in a heat exchanger.
Solar-thermal systems offer a compelling economic rationale, with relatively low initial capital costs and relatively quick payback. As you'll learn below, there are two types of solar hot-water systems: Active Systems and Passive Systems.
ACTIVE SYSTEMS
Active Systems are the more complex of the two, using electric pumps and valves to move water around the system and transfer heat. This increased complexity generally is more expensive, but it also offers greater efficiency over the long run. Active systems may also provide overall better performance than passive systems, and are typically a better solution for retrofitting an existing home (active systems are modular and do not need to be installed in a single location).
Active Systems fall into two sub-categories: Closed Loop and Open Loop.
Closed Loop systems, as their name implies, use a closed system of fluid transfer to heat up hot water, while not actually running the potable water through the solar collector system. Instead, the solar collector heats up an anti-freeze mixture that is then pumped through a heat exchanger in a water tank to heat up potable water. These systems are designed for colder climates, where freezing temperatures and harsher conditions exist. They also have higher maintenance costs than some of the other systems.
Open Loop: Open Loop systems are simpler because they just route potable water through the solar collector to be heated and then into the storage tank for household use. Essentially, these systems eliminate an entire set of pipes and fluid transfer, lowering costs and complexity.
PASSIVE SYSTEMS
Passive Systems generally also come in two flavors: one is Integral Collectors Storage, or ICS; the other, called Thermosyphon, is more widely used. The beauty of the passive systems is their ease of use, low maintenance requirements, and ability to function without any electricity.
Thermosyphon Systems rely on natural convective circulation of water: hot water rises above the cold, and can then be collected in a tank. Cold water in the tank flows back down into the solar collector panel to be heated and circulated. Systems like this have been in use for many years, and can be found in many Mediterranean countries.
Finally, it's important to remember that solar thermal systems are one of the easiest and most affordable ways to incorporate renewable power into your home or business. The upfront costs associated with the purchase of a solar water heat system are considerably lower than those associated with a solar PV system.
Regardless of which technology interests you, one of our certified solar professionals in your area can help walk you through the numerous options.
CONCENTRATED SOLAR
Concentrated Solar uses reflectors to concentrate the sun's rays onto a collector. The collector either stores the heat energy or uses a heat engine to convert it into mechanical energy.
The range of applications of this technology is enormous, and varies from the small solar cookers, which are becoming popular in developing countries, to vast fields of utility-scale mirrors, such as those employed by Solar Tres, a concentrated solar power (CSP) project slated for construction in Spain. This installation will focus hundreds of times the sun's energy on a single collector tower, producing 5 megawatts of electricity using liquid sodium as a heat exchanger. Additionally, it will have the fringe benefit of being one of the very few renewable energy technologies to come out of a James Bond Movie. Take that, Biomass!