Heating:

Active Solar Systems





Open Loop Pool heating Sys. Source: ThermoDynamics
Source: Solar Inspections
(1)
Evac. Tubes Source: Veissmann
(2)
Source: Solar Inspections
Batch Collector Source: Canadian Energy
A solar system is composed of Four main parts:

This is the part that absorbs the solar energy. They are either pressurized and always contain fluid, or a drainback system which is empty of fluid when not in use, or a combination of the two: a draindown system which is pressureized but is emptied when colder weather endangers the collector of freezing. Common forms of collectors are flat plate, batch, evacuated tube and transpired.

Flat Plate is the most common, it consists of a translucent or transparent cover with small tubes filled with water or antifreeze solution circulating over a black absorber plate that radiates heat into the tubes and the fluid is fed by gravity or pumped into the building.

Batch (aka breadbox) contains an insulated tank that is lined with glass and painted black on the outside to absorb the sun. Cold water comes in, is heated and held until needed, then the heated water is supplied to the building. Typically mounted on roofs or in sunny places on the ground for optimum energy efficiency.

Evacuated Tubes are parallel rows of transparent tubes, usually made of glass, filled with an absorber tube with low emissivity that heats the antifreeze solution inside. These are not as common but are very efficient due to the low amount of heat loss.

Transpired collectors are large south facing walls covered in a dark sheet metal in order to heat the air outside the building, which is then drawn into the space through perforations in sheet metal.

This part of the system transports the heated fluid or water from the collector to either the storage tanks or directly into the building to be used. Also included in this component are the freeze safe valves(2), that are connected to the return flow into the building on an uninsulated pipe off shoot (1), as pictured to the right.

The storage tank is where the heated potable water is held until it cools down enough to need to be recirculated or until it is needed inside the building. The tank can be an direct system or an indirect system, see next Sub-Topic "System Types" for more information.

Final piece of the total system, located inside the building. This device can do different things depending on the usage of the solar system. If the system is used to preheat ventilation air it is used similar to a thermostat, and in a Domestic Hot Water (DHW) system it can connect to both the solar powered system and the conventional system to shut off that system to save energy when the solar power is enough for the building's demand.

There are two major types of solar systems, one is passive where no energy is used to heat a space, an example is a green house, the other system is what is focused on here: ACTIVE. In the active solar thermal systems there are four basic types:

How it Works: the collector heats the fluid (either water or antifreeze) and it rises to the storage tank. Heat Flow Methods: Convection to tranfer fluid from collector to storage. Radiation to transfer heat. Benefits: Reduce use of conventional systems Drawbacks: System is not ideal for all climates Climate: Most ideal in climate with large amounts of sunlight, and infrequent freezing conditions Building Orientation: Best with a southern facing roof/collectors to maximize solar intake Typical Use: Ventilation preheating, DHW (Domestic Hot Water), Pool Heating

How it Works: takes potable water directly from water system and pumps it through collector during useful hours of solar radiation on an open loop, then back into storage tank or into the building if needed. Heat Flow Methods: Convection to transfer fluid from storage to colletor. Radiation to transfer heats. Benefits: Reduce use of conventional systems Drawbacks: Recirculates heat in order to avoid freezing Climate: Most ideal in climate with large amounts of sunlight, and infrequent freezing conditions Building Orientation: Best with a southern facing roof/collectors to maximize solar intake Typical Use: DHW, Pool Heating

How it Works: takes antifreeze solution (glycol based) and pumps it through collector during useful hours of solar radiation, then back into storage tank on a closed loop to heat up the potable water Heat Flow Methods: Convection to transfer fluid from storage to colletor. Radiation to transfer heats. Benefits: Reduce use of conventional systems Drawbacks: Recirculates heat in order to avoid freezing Climate: Most ideal in climate with large amounts of sunlight, and infrequent freezing conditions Building Orientation: Best with a southern facing roof/collectors to maximize solar intake Typical Use: DHW, Pool Heating

How it Works: takes air and pumps it through collector during useful hours of solar radiation, then back into storage tank on a closed loop to heat up the potable water Heat Flow Methods: Convection to transfer fluid from storage to colletor. Radiation to transfer heats. Benefits: Reduce use of conventional systems Drawbacks: Air looses more heat energy than fluids Climate: Most ideal in climate with large amounts of sunlight, and infrequent freezing conditions Building Orientation: Best with a southern facing roof/collectors to maximize solar intake Typical Use: Ventilation Preheating

Components of an Active Solar System. Source: Heliodyne
Indirect System. Source: Solar Inspection
Storage Tank Source: Veissmann
System Types
Photo Source: SolarWright
Active Solar Heating Systems are used in several ways to reduce the burning of fossil fuels, although these systems typically have conventional systems as back up.

Conventional Systems have a hot water heater that contains a burner that heats the water, this burner consumes energy either from electricity or propane, oil or natural gas. In a standby- tank system the tank constantly is holding hot water, thus consuming energy even when hot water is not in use.

Heating, Ventilation, Air Conditioning (HVAC) systems commonly take up the role of space heating or ventilating air into a space. These are typically large consumers of energy to power chillers, boilers, fans and coils as well as other equipment, all powered by consumption of electricity, oil, or natural gas in many cases.

Commonly pools are heated using a heat pump powered by electricity or gas, sometimes pool covers are used to raise the temperature. To raise the pools' temperature one degree Fahrenheit costs around 10-30% more energy than to maintain the temperature.

Types of Use
System Components
U.S. Energy Information Administration, Household Energy Comsumption and Expenditures 1993, and RMI calculations 1999. Figures are based on a typical single-family house of average size (2,280 sq ft) in an average climate region of the United States. source: RMI
The goal of any solar powered system is to reduce the need to purchase resources outside of the home. The Active Solar Heating Systems in particular are to reduce the load on conventional heating systems, which create more waste than a solar system. Examples of conventional power include:

System Objective
Space Heating Energy Consumption, Cost, and CO2 Emissions in a Typical Single Family House '97