One of the most complicated components to size in any solar thermal installation is the pump (or pumps if your chosen schematic requires more than one). All solar thermal pumps are centrifugal models, using vanes or paddles which spin within an enclosed space to create pressure. Your choice of pump will depend on the type of system and two measurements: flow and head.
A solar thermal space heating installation with storage is one of the most complicated systems to size. There are so many variables: storage size, collector array size, expansion tank size, piping size, heat exchanger size and heat load requirements. There are two ways of working out how big everything needs to be: the complex mathematical way or by rules of thumb.
Space heating with solar thermal installations revolves around Btus. If you've sized the heat generation part of your system already, you'll be familiar with this. The next step is to work out how big the collector array needs to be.
The oldest, simplest and most common solar thermal collectors are flat plate collectors. They have a robust design that can withstand temperatures falling well below zero and rising well above most climate norms (they work fine at around 180°F or 82°C). It's no surprise that they're the base to which all other, more complex collectors are compared.
Flat plate collectors are the simplest type of solar thermal collector. They consist of several basic parts, as described below.
An inverter's surge capacity indicates how it handles short-term overload before "tripping". Surge capacity is essential to start up some large loads, especially motors that need 2-3 times their running power to get going. The start period may be very short – a fraction of a second – but it still needs to be considered.
An unsuitable backup power supply is the Achilles' heel of an off-grid energy system. The problem does not lie in the renewable energy equipment's reliability; a well-designed system is often more reliable than the electrical grid.
Problems are more often related to the weather than the equipment. When the winter months are dark without any sun or wind, your system will require more batteries.
A genset unit is durable and long-lasting if it is maintained well. A good quality generator has no problem with run times but it should be maintained regularly. For example, a diesel engine may need servicing at various hour intervals, such as 25, 250, 500 and 1,000 hours of operation.
Why is a battery bank necessary? Because an off-grid system does not allow you to store electricity easily and economically. There are other ways to store electricity but they are more expensive.
The more energy you consume, the bigger the storage facility you need. Buckets are measured in liters or gallons; battery capacity is measured in watt- or amp-hours. If the battery uses a higher voltage source for charging (like a full-strength PV array), you will enjoy a higher voltage recharge – a battery bank of 24V can record a 30V voltage when it goes through equalization charging.
