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What is Active Solar Heating?
A simple concept for solar heating is the use of cladding material on south-, west- or east-facing walls. Small gaps enable air to flow in from outside. In the daytime, air passes across the solar panels as well as along their inner surfaces, absorbing the sun's rays to warm the air, causing it to rise. This hot air is drawn into the ventilation system of the building, reducing the load on the heating system. On hot days, such systems can heat air by as much as 30-50°F (17-28°C), depending on the rate of flow.
Photovoltaic System Grounding
Grounding is used to dissipate electrical energy safely when faults occur. This is the third pin on your extension cord plug which allows electricity to flow when system insulation fails.
Basic Principles of Solar Thermal Systems
As soon as you start looking into a solar thermal installation, you will run into certain terms and principles that may be unfamiliar. It is essential that you understand these ideas, so that you can see what is needed and make intelligent decisions when offered choices by professional installers.
Pressurized Solar Thermal System Pumps
One of the advantages of a pressurized solar hot water system is that the solar loop is always full. This means that the pump has no static head pressure to overcome (just friction head), so low-head, slow-starting pumps can be used effectively. And those pumps can be run on power from a PV array, eliminating your grid-tied power costs for operation.
What are Drainback Solar Thermal Systems?
Drainback solar hot water systems are not as flexible as pressurized systems, but still work very well in both residential and business applications. They are very efficient if they are planned and installed carefully.
Drainback Solar Thermal System Pros and Cons
These systems have many advantages:
- They can use simple water as a solar fluid for lower cost.
- They are very efficient if they are planned and installed properly.
- They are ideal where the installation will lie idle for extended periods.
- Since the system empties when it switches off, the solar fluid has a long life.
It's also important to consider these disadvantages:
Drainback Solar Thermal System Tanks
Drainback installations use three tanks to heat the domestic water supply. The two main tanks are just like those used in pressurized solar thermal systems. However, the third is specialised – the drainback tank, which is installed on the solar loop.
The two main tanks are installed in standard fashion: the one heated by solar energy is piped in series before the backup grid-tied tank, so that the sun-heated supply is topped up with heat in the second tank if necessary.
Drainback Solar System Pumps
Unlike pressurized installations, drainback solar hot water systems have a fair amount of head to overcome before they start operating properly. Consequently, they need more powerful pumps. The choice of pump is absolutely critical to the system.