Solar Hot Water Systems

There are many things to consider when implementing a solar water heater; the following step by step guide outlines a number of the considerations and challenges involved with installing a solar water heater.

Step 1 - collate the facts

From the outset you have to decide,

• What is my Daily hot water usage?
• What size storage capacity do I have/need?
• What position will my solar collectors be in? 
• What is the climate do I live in? 

Step 2 - How much power

The two main variables to consider here is the size capacity of the hot water store and the surface area of the solar collectors.

The Solar Store

A family of 4 people uses on average between 150 - 230 (35-55 per person) litres of hot water a day, therefore your hot water store should cater foryour families daily hot water usage. You will need to carry out your own tests to make sure the amount of water required can be stored.

The Solar Collector

Now that you have worked out your daily hot water consumption you can start to calculae the area of the solar collectors needed.

The basic rule is that 1 square metre of solar collectors roughly covers 50 - 65 litres of hot water. Remember this varies because of climate factors and the positioning of the Solar collectors.

When you buy solar collectors remember that they are sold in modular sizes varying from 1m to 4 metre squared.

Step 3 - What System

Solar Collector vary considerably from one make to another, there are websites which publish lists of the best performing solar collectors. Once you have selected a particular make, try not to mix these solar collectors with collectors from another make, the variance in quality between the collectors can affect your whole system.

Other things to consider,

• Can the solar collector be switched off 
• What will the Solar collector look like on your roof
• Is the solar collector produced y a reputable company that environmentally friendy in terms of its production & transportation 

Step 4 - Maintainance of System

Freezing can cause permanent damage to your solar collectors and hot water heating system; you need to protect them with the following measures, 

• Insulation – this can reduce the affects of freezing
• Non toxic antifreeze – is available to treat your solar hot water system
• Drain Back – allows the fluid from your solar collectors to be automatically drained where necessary
• Freeze resistant piping – new designed pipes that don’t get damaged when frozen

Step 5 - Heath considerations

Although unlikely, it is possible that the water going through your Solar Hot water system could get contaminated. The best way to ensure that this problem doesn’t materialise is to make sure the water is heated above 55 degrees, before reaching taps, washing machines, showers etc

Solar Hot Water Systems can also provide water which is too hot and therefore dangerous; in this case your hot water store can be fitted with a mixed valve allowing cold water to cool the water.

Step 6 - Add or Replace

This is often a trade off between space and efficiency.

It is common for solar collectors to be connected to the existing hot water tank. This is perhaps the most straight forward method as you don’t have to find space for another hot water store. While this might save on space it can often be at the expense of the efficiency of your solar hot water system. The current hot water tank may not be insulated to the required standard plus the auxiliary hot water supply may not work well in tandem with your solar hot water system. 

Having an additional hot water supply can alleviate some of these problems; you can simply join your existing storage tank to your new solar storage supply. This can be done by diverting the cold feed from the older tank into the bottom of the new tank. The new tank is fed by a pipe at the top of the older tank. 

A perhaps more efficient way is to have one bib tank which is subdivided into sections in order to take a hot water feed from different heat sources (e.g. solar, electric, gas)

Step7 - Solar Collectors - implementation

Of key importance is where the solar collector is placed on the roof & How you do this, for a number of reasons,

• Solar panels must be in line with the roof tiles, in order for it to ascetically viable.
• Placed in an area with little or no shading.

You can download a best practice program for solar design in your home from http://www.thecarbontrust.co.uk/ 

You can also apply for a government grant for solar power, see http://www.est.org.uk/ or call 08009157722