Our Services - Solar Space Heating
Solar thermal systems can be used for a variety of heating applications. In Wisconsin, they are most often used for domestic water heating but can also be used to provide energy for winter space heating loads. Even here in Wisconsin, using the sun's energy can save money on winter heating bills. Heating a home or business with solar energy generally requires a larger array of collectors and in some cases a larger storage tank than for domestic water heating.
A solar space heating system may be able to tie-in with an existing boiler or furnace, or the system can stand alone and deliver heat through its own heat emitters. Heat emitters that work well with solar space heating systems operate at low temperatures (less than about 120 degrees F), and include most radiant floors, fan convectors, some panel radiators, and some fin-tube baseboard radiators. The planning phase of new construction is an ideal time to think about how to implement solar space heating, but these systems can often be retrofitted effectively as well.
How it Works
Our solar space heating systems are hydronic, meaning that they use liquid (water or glycol) to collect and transfer heat, as opposed to air.
Whatever type of heating system and home you have, Full Spectrum Solar has the knowledge and skills to provide you a customized system to maximize comfort and efficiency. Our staff of experienced engineers guide you through the available options and provide a complete system design to meet your goals.
There are three basic techniques to provide space heating in northern climates using solar thermal collectors:
Direct Solar Heating
Direct solar heating systems are the simplest and least expensive solar space heating systems. There is no storage medium for the collected solar energy other than the thermal mass that already exists in the house. On sunny days during the heating season, the heat is simply transferred into the house as it is collected. As a simple rule of thumb, direct solar heating systems can provide up to 25% of a home's heating requirements in southern Wisconsin by using one square foot of solar collector for every ten square feet of the home's footprint area. Additional collector area may be added for multi-story homes.
An ideal application for a direct solar heating system would be concrete or gypcrete floors with PEX tubing installed for radiant heat. These floor materials contribute thermal mass in the home and are capable of holding a lot of heat without the home's temperature drifting too far from the desired point. Solar heat collected during the day is released into home’s interior during the evening and night.
A direct solar heating system can be a good option even if your home does not have radiant floor heating. Another example of a good application would be a house with an addition on the north side that is under-heated on the coldest days of the winter. The rest of the house warms up and the thermostat turns the furnace off, but the north side addition is still cold. The coldest days are often clear and sunny in our climate, and a direct solar heating system could provide heat to the addition when it's needed most and bump up the temperature to a more comfortable level. This type of solar heating system could tie in with the furnace ductwork or use a dedicated heat emitter such as a fan convector or low-temperature panel radiator.
Water Storage Solar Heating
A water storage solar heating system stores collected heat in a water tank, which is similar to a domestic water heating system. After the heat has been delivered to the storage tank, it can be distributed to the home or building. The tank volume can sometimes be relatively large, but it depends on the system and many systems are designed to be effective with only a small amount of additional storage.
Water storage solar heating systems are able to accommodate more collector area than direct solar heating systems, so they can provide greater portions of the winter heating loads. Another advantage is that the water storage allows for highly adjustable heat draws, allowing for more efficient use of the heat and greater control. The rule of thumb for a water storage solar heating system is it can supply up to 50% of a home's heating requirements for a home in southern Wisconsin by using one square foot of solar collector for every four square feet of the home's footprint area. Additional collector area may be added for multi-story homes.
Almost any home could be a good candidate for a water storage solar heating system. A prime example is that many of our customers work some level of passive solar into the design of their homes, but want to do a little more with an active solar heating system. In this application, a water storage solar heating system would be a good selection because the system would be capable of storing the collected heat during the daytime - the same time that the passive solar is already heating the space - until nighttime or a cloudy day.
High Mass Solar Heating
In this type of system, instead of storing heat from the solar collectors in a water storage tank, the solar energy is stored in an insulated, compacted sand bed that is usually 2- to 3-feet deep and is located directly under the building. This technique is limited to new homes or home additions. Collected heat is delivered to and stored in the sand bed using a gridwork of pex tubing. Homeowners with high mass solar heating typically begin storing solar heat in their sand beds during late summer or early fall. When the sand bed becomes warm, and outside temperatures drop, the stored heat will slowly rise up into the building, warming the floors and the whole building (provisions for air movement between the floors may need to be provided). These systems can provide up to 75% of a home's heating requirements for southern Wisconsin by using one square foot of solar collector for every four square feet of the home's footprint area. Additional collector area may be added for multi-story homes.
While high mass solar heating systems are generally the most productive, the heat delivery to the home - by design - is relatively uncontrolled. It is not unusual for the home's temperature to vary by several degrees during warmer or cooler stretches of weather. For example, we often get a hot stretch of weather in September or even October after heat has begun getting stored in the sand bed. The home can feel uncomfortably warm until cooler weather arrives. A high mass solar heating system is not a good fit for the homeowner who is going to run their air conditioning during these times. This specific type of system is best for homeowners who can tolerate a temperature swing, actively participate in their home's heating and cooling systems and cooperate with the weather. Otherwise, it is better to consider a direct or water storage solar heating system.