Questions about Solar Hot Water Energy
A solar hot water system can produce hot water under cloudy conditions although at a diminished capacity when compared to a sunny day. When designing a system for a specific location, the insolation value or average annual sun hours per day for that location should be considered to construct and position a system that will maximize the available sunlight. A supplemental electric, oil or gas fired heating system is typically maintained as a backup for longer periods of low-light conditions.
The winter-time productivity of a solar hot water system installed in the northeast can approach summer productivity levels. While there are fewer sunny days in the winter and days are shorter, a properly designed and installed system can perform at or near its maximum BTU output capacity throughout the winter to supply hot water needs. Sunlight reflection off snow cover can enhance performance of solar collectors. Systems are designed and insulated to minimize heat loss between from the collectors to the storage tank(s)
For a typical residence in the northeast, a solar hot water system can provide 50 to 75% of hot water needs annually. It is likely that the system will provide close to 100% of hot water needs during the summer months. Residential solar hot water systems are typically sized based on the number of occupants in the house and available roof space for the solar collectors.
Not necessarily. An external brazed plate heat exchanger may be used in conjunction with an existing hot water tank provided the tank is of sufficient capacity to handle hot water generated by the solar system. A heat dump is often necessary when hot water storage is insufficient to handle the output of the solar collectors. In most cases, the solar hot water system will require a dedicated storage tank either as a stand-alone unit or as a pre-heat tank for an existing hot water system. Pre-packaged systems typically include solar collectors and appropriately sized solar hot water storage tanks.
Flat plate collectors have a classic ‘solar panel’ appearance. These collectors are most productive and efficient in southern climates. Evacuated tube collectors have been shown to out perform flat plates in the colder climate of the northeast. Flat plate collectors are typically less expensive than evacuated tubes and are considered by many to be more aesthetically pleasing. However, for solar hot water heating in the northeast, payback periods and return on investment for evacuated tube systems often makes these systems more financially attractive than flat plate systems.
Yes. The same 30% Federal Tax Credit that applies to photovoltaic systems also applies to solar hot water systems. Commercial clients can also take advantage of 5-year accelerated depreciation on the installed cost of a solar hot water system. For residential consumers, the Commonwealth of Massachusetts offers a personal tax credit for installation of a solar hot water system and a tax exemption on the value added to the residential property by the system. Additional incentives may be available through local utility providers.