Solar hot water systems have been accepted in most countries for many years and are widely used in Greece, Turkey, Israel, Australia, Japan, Austria and China. Because this technology has proven itself so well, it is an easy first step to begin the shift to renewable energy in the home.
Often, the biggest consideration in considering this option is the size of the initial financial outlay for solar water heating systems. Offsetting this expense can take several years.
On the other side of the equation is the fact that once the system is paid for, solar energy is free, thus greatly reducing the system operating costs, whereas other energy sources such as gas and electricity can be quite expensive over time, and their cost is only expected to rise.
Thus, when the initial costs of a solar system that is properly financed are compared with other energy costs, in many cases the total monthly cost of solar heat over the lifetime of the system can be much less than other more conventional types of hot water heaters.
The family of 5 in the following case study financed their system with a low interest energy loan, now common in many states. After the system was in service for 2 years they computed their average monthly bill and compared it to the 2 years of bills before their system was installed. Fortunately, they had kept accurate records of their energy bills, which allowed the performance of their solar thermal system to be accurately analyzed.
It turns out that their monthly savings of roughly $80 per month counterbalanced their $80 monthly energy loan payments. The life of the loan being 7 years means that after the loan is paid off the system will have completely paid for itself and the family is left with a cost free energy generation system, which will last another 15 – 25 years. With results like these, the initial cost of purchasing and installation these systems is easier to justify.
This kit includes a circulator pump, all of the necessary check valves, temperature gauges, valves, and boiler drains for a single tank solar loop, a pressure relief valve, a flow meter, an automatic high vent, an expansion tank, and nipple adapters so the unit can be mounted directly on the tank – and a choice of mounting systems to fit any installation site.
The manner in which this system is plumbed is common for this area of the country in that the house’s boiler is used as a backup heating source for the domestic hot water. The most energy efficient way to use a boiler for backup when it is plumbed directly to the upper heat exchanger is to utilize what is called a cold start boiler rather than a tankless coil boiler or a boiler with a hot water coil.
The latter two types of boilers keep a receptacle of water at a very high temperature whether or not there is a need for it. Whereas the cold start boiler will not consume any energy unless there is a call for heat from either the hot water tank or one of the heating zones.
If the site in which a solar thermal system is to be installed has one of the tankless coil types of boilers it is possible to use slightly more complicated plumbing strategies, which utilize the circulation port on the Stiebel Eltron SBB series tank to minimize energy consumption.
It is also possible to convert a tankless coil boiler into a cold start boiler in many cases. This Shelburne Falls family originally had a tankless coil boiler that they used for backup during the heating season, and a standalone electric hot water heater that was plumbed in series with the solar storage tank during the warmer months. When the electric tank went bad they had their tankless coil boiler converted into a cold start boiler, optimizing their energy savings.
Case Study System
Specifications: SOLKIT 3
The SOLKIT 3 is fairly typical for families of 4 or more in the Northeast, as it commonly achieves a solar fraction of 70 – 85%.
The kit consists of the following components
- 3 SOL 25 + collectors,
- 108 gallon dual heat exchanger storage tank
- Differential controller
- Flowstar pumping station kit.
GET Aug2011 page 12