Solar Heating System For domestic Hot Water

A solar heating system is a great way to use solar panels to heat your domestic hot water.

If it all sounds too good to be true, there is a little pain involved with solar hot water systems in the form of the initial outlay.

The supply and installation of solar thermal panels can seem expensive, although the prices of the various types of panels are coming down all the time. A typical 3 panel solar thermal system should cost in the region of £2,500 - £3,500.

As with any renewable technology, the more people who install them, the cheaper they'll get. However the day when you can install a hot water system for a few hundred pounds is still some way off.

Solar Heating System

Although the initial install cost is substantial, you need to think long term. A solar heating system (as with any green technology) is an investment. So you need to consider the following:

  1. What will your initial outlay be?
  2. What will it save you annually?
  3. What is the payback period?

Whichever type of solar heating panel you choose (there are two main types) you will also need to budget for installing a larger twin coil hot water cylinder to transfer the heat from the panels to the hot water cylinder.

In the UK's climate solar panels will not provide all of your hot water requirements.

If sized correctly your solar hot water system can provide up to 70% of your hot water needs, so you'll need to boost it with a secondary heating system (oil or gas boiler, a wood burning stove or a heat pump etc.)

Twin Coil CylinderTwin Coil Hot Water Cylinder

Types of Solar Heating System Panels:

There are two main types of solar thermal panels on the market and each has it's own pros and cons. Although truth be told they both do the same thing so it's entirely down to personal opinion as to which you go for.

1. Evacuated tube panels:

  • These are made of multiple sealed double layer glass tubes with a vacuum inside. Each tube houses a U-shaped copper pipe, through which runs a fluid. The Sun’s rays heat this fluid which is pumped along pipework to your water cylinder where it circulates around a second  coil (a stabndard cylinder only has a single coil) to heat your domestic hot water.
solar heating systeEvacuated Tube Solar panels
  • Evacuated tubes have a greater surface area exposed to the sun due to their cylindrical shape and a reflective panel behind the tubes.
  • Some argue that they perform better in our overcast climate although others say they heat the water too much in the summer months. Plus, they are relatively easy to damage, although the tubes can be replaced individually.

2. Flat Panel system:

  • This solar heating system does not use evacuated tubes. Instead a flat panel of solar glass covers an absorbent plate which has small metal pipes to the underside and then several layers of insulation material.
Flat panelFlat Panel Solar Panels
  • The flat panel system is less fragile than the evacuated tubes, but they currently cost a little more.
  • Visually, they are less intrusive, especially if you have them flush mounted as in the image above (much easier with new builds or roof cover replacements rather than retro fit installations). On a new build or reproofing project this method also means you'll need to buy fewer roof tiles.

Regardless of which type of solar thermal panels you think are right for you it's also important to understand the advantages and disadvantages of solar energy before you commit to either.

Depending on who you talk to, you'll get differing opinions on the two types.

Many people say the flat panels can be affected by condensation (although some manufacturers have addressed this by drilling ventilation holes to help reduce this).

Others will say the evacuated tubes heat the water too much in the summer months. However if you take an average of both systems over a full year, there isn't a huge difference between them.

Of course you could fit photovoltaic solar panels (produce electricity as opposed to hot water) and then link them to your electric immersion heater to achieve the same domestic hot water in addition to free electricity.

Now all you need to do is decide which type of solar thermal panel is right for you..

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