SOLAR What Size is the collector? The 10 tube double-walled tube collector (47mm tubes) is 1760x xxx x130mm (LxWxH) The 20 tube double-walled tube collector (47mm tubes) is 1760x1500x130mm (LxWxH) The 30 tube double-walled tube collector (47mm tubes) is 1760x2170x130mm (LxWxH)
The 20 tube double-walled tube collector (58mm tubes) is 1900x xxx x200mm (LxWxH) The 30 tube double-walled tube collector (58mm tubes) is 1900x xxx x200mm (LxWxH)
The 10 tube single-walled tube collector (70mm tubes) is 1700x1000x130mm (LxWxH) The 20 tube single-walled tube collector (70mm tubes) is 1760x xxx x130mm (LxWxH)
Are The Tubes Fragile? The tubes are made from borosilicate glass, which is very tough (also known as pyrex). The tubes are designed to withstand hailstones up to 35mm - so they are unlikely to be broken, unless dropped onto a solid floor prior to installation.
What size solar cylinder should I fit? heated with 2 or more panels, and it is possible to add an extra panel to benefit from higher temperatures in the winter. In fact, if you fit a smaller cylinder, you will We recommend that the 20tube panel is used with cylinders up to 175litres, and the 30tube panel is used with cylinders up to 260litres. Larger cylinders can be have hotter water, but of course less of it. We would recommend fitting a tank of heated with 2 or more panels, and it is possible to add an extra panel to benefit 135litres if you prefer a smaller amount of hotter water.
What is the output of the panel in terms of kWh? This varies according to the time of year - in summer we get almost 10times the amount of solar energy that we do in the winter. In the summer, you can expect to get 14kWh of heat per day from a single 20tube panel, whereas in December you can expect only 1.15kWh per day on average. Even in the winter, it is possible to preheat the water to 40C or more if the sun comes out. In fact, if you fit multiple panels, it is possible to heat your hot water to 100C in January (we have seen this in Cornwall).
How hot will the water get? This depends on the size of the cylinder you chose, and the amount of water you use. A smaller cylinder will be heated to higher temperatures, whereas a larger cylinder will heat more water, but not to the same extent. Systems are generally designed to heat water to 65C or so, although during the winter, it may be necessary to 'top-up' the heat on less sunny days. Large arrays, running high temperature solar antifreeze at high pressures can be designed to achieve temperatures of 170C or more!
Where do these need placing and at what angle? Panels should be sited on a south facing wall or roof. In fact, anywhere between South-West and South East will give good results. If you are limited to an East- West facing system, then you will need two panels to provide the same amount of hot water as a single south-facing roof slope. The most frequent solution to this problem is normally to mount one panel on the east slope and a second panel on the west slope. A special controller is available for East/West facing installations.
The panels should be mounted at the angle of your lattitude. For example, at our location in the UK, this is 53˚. This is AVERAGE optimum angle. In fact, in winter the optimum angle is 15˚ steeper, whereas in the summer it is 15˚ shallower. The panels will function anywhere between 15 and 90˚ angle of inclination. This is actually academic, a variation of 15˚ will make very little difference to the output, so most people simply settle for whatever angle their roof slope is. The extra cost of trying to stand panels off the roof to achieve better efficiency would probably be better spent on purchasing a second panel!
Does the roof need to be strengthened at all? The solar panel in operation weighs around 50kg - this is really not much weight for a roof, when you consider the weight of the tiles or slates. Generally there is no requirement to strengthen a house roof prior to mounting the solar panel, except if you are fitting a panel to a very old roof, which has sagging and decaying timbers.
Are spares available? Yes, spares are always available, should you need them. With no moving parts, it is very unlikely that you will need to replace anything, but occasionally customers break tubes during the installation process, in which case you can purchase a modestly-priced replacement. However, it is not possible to post a replacement tube, so you will need to collect it. The tubes are made of borosillicate glass (aka 'pyrex') so they are actually very tough.
Are the panels guaranteed? Yes, we offer a 12month guarantee, although, with no moving parts the panels are extremely long-lived, probably in excess of 25years. In fact, the manufacturers offer a much longer guarantee, but in the UK we do not offer this extended period due to the legal requirements - if we were to offer a 25year guarantee, we would need to take out an 'indemnity' policy on the product. The insurance company would cost this in at probably £300 per item. The cost is out of line with our policy of keeping prices as low as possible, and We decided that most customers probably would not want to pay this additional fee!
Can I fit this system DIY? Yes you can! These systems are very easy to fit, and anyone with basic plumbing and electric skills can carry out a DIY installation. Mounting the panel on the roof is sometimes daunting, although it is actually quite simple - but we can offer this service, if required.
What if I have a combi boiler? Have a look at this page - where you can also find a light-hearted alternative!
Will the system need to be inspected by a plumber or be installed by a plumber? No, you can do this yourself. However, you can call in a plumber to carry out the work if you feel you are not able to tackle to plumbing yourself. We normally recommend that you fit a pressurised system. This is not essential, but it allows you to place the solar panel on the roof without worrying about whether it is possible to place the header tank high enough to function correctly. With a pressurised system, the plumbing is simpler, and by running the system at 1-2bar, it is possible to increase the boiling point of the water to 120C or higher - allowing greater safety margins, and lower chance of fluid loss.
How much maintenance do the systems require? Very little maintenance is required for solar water heating systems. You should occasionally check the system pressure, to make sure there has been no water loss, and to check for any air in the system. The only other requirement is to ensure that there is an electricity supply connected at all times, otherwise without pump circulation, in strong sunshine, the panel could overheat, and start to boil off water.
What about freezing in Cold Weather? The solar panel is very well insulated - the manifold is surrounded by 2"of rockwool insulation. This is better than your outdoor water pipes, so it is unlikely to freeze except in exceptionally cold weather. However, it is recommended that you take precautions to prevent the possibility of freezing, by either adding antifreeze to the system (use a non-toxic solar antifreeze) or you can use a DELTASOL B controller which has 'freeze protection' - this controller monitors the temperature of the collector - and if it falls below 4C, it will turn on the pump, allowing water to circulate and heat the manifold. You should turn this function off if you use antifreeze.
Can I use Solar Power with a Mains Pressure Hot Water Cylinder? Yes. There are two ways to achieve this. You can either purchase a mains pressure unvented water cylinder (these can be expensive). Please note that you will have to have a pressure vessel certificate to install these. Alternatively, you can fit a 'solar store' cylinder (see below)
What is a Thermal Store? A thermal store is a tank which has an additional large surface area high efficiency coil fitted. The mains cold water is fed into this coil, thus heating the water on its way through. The mains water exits the tank as hot as the hottest water in the tank, but without losing any pressure - thus providing mains pressue hot water to the household taps.
Can I get a grant for these systems? Grants are only available for professionally installed systems. At the moment, our panel is undergoing testing for the solar grant. However, this will take several months, and costs in the region of £15000. The government has refused to allow a UK laboratory to carry out the required tests - so we are forced to use labs on the continent - which pushes up the cost of the exercise. Once we have carried out the required tests, the price of the panels will have to increase to cover the investment. For this reason, it is likely that the grant will not make the solar installation any cheaper. solar installations are available at £2500, whereas the grant-aided systems are generally £6000-8000, with a £400 grant!
Do I need planning permission? In most cases, no. Evacuated tube solar panels are considered in the same way as roof windows. Unless you live in a listed building, it is unlikely that it will require planning permission. Even if you do live in a listed building, you can usually fit the panel to the rear of the building, or at ground level without requiring planning permission
Can I power the pump with solar energy? Yes, this is possible. For flat plate collectors, manufacturers will specify a 5W photovoltaic panel, and a 5-10W low voltage pump. This is because flate plate collectors do not work efficiently in low sun conditions, so the pump only needs to function in bright sunlight. This is insufficient for evacuated tubes, which due to their high efficiency, will require pump circulation even in overcast conditions. For this reason, the pump should be rated at least 10W, and the panel 20W to provide sufficient circulation. At the moment, there is no cost-effective low voltage pump on the market suitable for pumping hot water. The most popular 12v solar pump, the 'ivan' retails at around £150-200, making this an expensive option. It is possible to use a solar photovoltaic panel to drive a mains inverter, powering a standard 220v circulation pump, but most customers do not want the complexity of such as system.
What is the difference between the single-walled and double-walled solar panels? The difference relates to the design of the solar tubes. The standard tubes are double-walled, with a vacuum between the two walls of the glass. The centre is filled with air and the heatpipe runs up through the centre. The single walled tube is entirely filled with vacuum, and the vacuum is sealed by a glass-metal weld sealing the heatpipe to the glass. This is technically much more difficult to do, hence the cost is much higher. The single walled tube has a marginal advantage over the double-walled tube in that it reacts much quicker to sunlight (eg it starts to heat water within 5-10minutes rather than 10-15minutes) - so it is slightly more efficient in marginal conditions. However, it also cools down quicker, whereas the standard tube will continue to heat for 10-15minutes after the sun goes in. A 10tube single walled panel (70mm diameter tubes) produces about 10% less heat than a standard 20tube double-walled panel (47mm diameter tubes).
How many panels/tubes do I require to meet my household needs? This is a difficult question to answer as it depends on your water usage. For example, one person that contacted us lives in a motorhome, and uses only 70litres of hot water over a two week period. A young couple I spoke to estimated their hot water consumption to be at least 400litres per day! First you should calculate how large a hot water cylinder you require to meet your needs. Remember that solar cylinders are normally designed to store water for use over 2 days, rather than one, thus allowing you hot water even if the following day is cloudy. Once you have calculated your cylinder size, you can estimate your panel size on the basis of One Solar Tube per 6.5 - 8.5litres of hot water cylinder (i.e. a 20tube panel can supply hot water for a 120-170litre cylinder, and a 30tube panel can supply 180 - 255litres). This assumes you have an unshaded south- facing roofslope to mount the panel
Can I heat my house with evacuated solar tubes? There is 10 times more sun energy in the summer than in the winter. (this is the reason for the different seasons, after all). Therefore you immediately have the problem that the bulk of the energy is at the wrong time of year. The other problem with using solar to heat your house is that it is not present at the times when it is really cold - at night, on very overcast days, in winter evenings etc. In practice you can provide a significant amount of supplementary heat in the spring and autumn (and some people have implemented such systems), but the contribution in the winter will be minimal, restricted to sunny days, but you will need to fit many more panels, as heating a house is a lot larger task than heating an insulated cylinder of water. Solar water heating on the other hand, can be effective even in the winter, as the amount of heat required is considerably less than that required to heat a house.