Solar water heating systems = Solar panels + solar energy. Solar thermal: solar power & solar hot water. MCS RHI Solar technology. PV pumped solar water heating systems.
Solar Panels For Water Heating Introduction: The Basics
Make the Most of the Sun’s Solar Energy With Solar Panels
If you are committed to helping save the environment whilst at the same time lowering your heating bills, you might be considering using renewable energy. New technology is now available that allows you to save money on your heating bills at very low impact to the enviroment. By installing solar panels on ythe roof of your home you can easily provide an effective, yet affordable means of heating water for use around your home and thus reduce your household’s consumption of fossil fuel derived energy.
UK and Irish applications of solar thermal
Are primarily domestic water heating (not central heating). There now follows some general information on solar heating.
Solar plumbing types.
There are three main types of solar water heating system plumbing: Direct, Twin Coil and Thermal Store. With Direct solar heating systems the water in the collector is the same as the water circulating in the tank and it comes out of the taps. These systems use materials which are approved for hot potable water. With conventional Twin Coil systems the antifreeze circulating around the system does not come into direct contact with the water coming in the tank or coming out of the taps. (If they have a raised backup heater they need a shunt pump for Legionella safety.) Thermal stores have a large heat-out heat exchanger which delivers mains pressure water. This allows them to pre-feed suitable combi boilers. For safety reasons, Solar Twin Ltd only offer Direct Plumbed Systems and Thermal Stores.
There are two types of solar water heating systems in terms of operational carbon footprint: zero carbon and low carbon. Zero carbon systems circulate fluid using solar electric pumps or by convection, also called thermosyphon. Low carbon systems use mains electric pumps and controls. These typically offset only 2-10% of the solar energy gained and 5-25% of carbon. For environmental reasons Solar Twin Ld offer PV pumped zero carbon solar heating systems only.
Solar heating components.
In general, domestic water heating systems consist of solar collectors containing a heat transfer fluid such as water or antifreeze, plus a pump, its control unit, connecting pipes, and a backup heat source such as gas, oil, electric immersion heater. A small photovoltaic panel may also be supplied. With direct hot water systems, while the existing hot water tank may be retained, a water softener may be needed. With twin coil systems, the exisitng single coil hot water tank is usually replaced. Thermal stores can either replace existing high or low pressure cylinders or they be added, where space is available for combi boiler installations. The general rule of reliability engineering is: the fewer components, the better. Solartwin is a simple PV pumped fully filled open vented system. It uses water as the heat transfer fluid and has a freeze tolerant panel.
The practicalities of having solar heating.
Some simple installations can be surveyed and specified by phone. Systems with have high pressure plumbing, mains electricity and replacement cylinders normally require on-site specification. Installing a domestic system usually takes 1-2 days. Maintenance varies with the system and engineer site visits are not usually required annually, but at 3-6 years intervals. Life expectancy is typically over 20 years, and at the end of its life most metals and glass, plus some of the polymers used in solar water heating systems are recyclable. Solartwin is uually surveyed by phone. Systems can usually be retro-fitted in less than one day to existing cylinders. Maintenance visits are needed every 6-7 years. Salt for a water softener may be needed for direct installations in hard water areas.
Solar size and performance.
The area of domestic solar hot water panels is typically 2-4 square metres. Most domestic Solar thermal collectors are mounted on a roof and are relatively forgiving about exact position, provided they are not facing north of east or west. Over a year an east or west facing roof collector will produce only 10-20% less than a the maximum, which is typically from a S facing collector at around 30 degrees pitch. Roof mounted systems tend to give solar fraction sof 30-60%. This is the percentage of water heating energy which is eliminated by using solar. Solartwin has a 2.8 square metres area panel. One panel is suitable for most homes of up to 4 people.
Solar performance trends.
In new build solar installations, there is an growing trend towards system optimisation rather than maximisation. Optimisation stresses delivering usable (rather than total) hot water. Here, the building is designed to accommodate due-south facing oversized steep collectors (from vertical wall mounted, to 60 degrees). Such systems give rather better winter performance, at the expense of what tends to be otherwise an excess of solar heat in summer. These systems’ flatter annual performance can deliver a higher solar fraction which, in UK, can be as high as 70%. Solartwin do this on certain new build projects.