Pressurized Solar Thermal System Pros and Cons
These systems have many advantages:
These systems have many advantages:
Pressurized solar hot water installations have a closed solar fluid loop that is always full of liquid. If the collectors get colder than the storage tank and are situated above the tank (as is usually the case), thermosiphoning can occur.
As the name suggests, a pressurized solar thermal system operates under pressure. In particular, the solar fluid circuit is always under a certain amount of pressure, which can vary enormously depending on the local climate and a variety of other factors. It is vital to understand the effects of pressure and how the system is managed to avoid catastrophic events.
Like any closed-loop installation, drainback solar hot water systems use a heat exchanger to pass energy from the solar fluid to the domestic water supply. However, drainback setups include a third, specialized tank – the drainback tank – which holds all the solar fluid when the system is idle. This fluid can still be very hot when circulation stops, so it makes sense to have a means of passing that energy to the domestic supply rather than waste it.
Integral collector storage (ICS) solar hot water systems are remarkably simple and cheap when compared to the other types. They don't use pumps, they don't need controllers, they use only one tank and they require very few extra components beyond a big water tank, some pipes and a pile of insulation materials.
A check valve is a simple device that only allows liquids to flow through it in one direction. These valves have an arrow marked on the outside to show the allowed flow direction. Two different types are used in solar thermal installations: "spring" and "swing" check valves.
All modern solar thermal systems use both vents and vacuum breakers. Vents are used to allow air to escape from a circuit that holds fluid and vacuum breakers do the opposite, letting air in when the internal pressure falls too low.
It doesn't matter whether you're looking at renewable energy from the point of view of saving money or saving the environment: solar thermal systems are a great way to take your first steps. As it happens, preserving the environment and reducing your bills often go hand in hand, although it may not be immediately apparent when you look at the cost of installing new systems!
Would it surprise you to know that the price you pay for fossil fuels could be as little as 20% of their real cost? That's because they're often subsidised by the government. Cynics would say that this is to keep prices low and ensure that business keeps booming for the people who control the resources and, in many ways, history shows they're right.