FAQ: Solar Water Heating


Q. What is solar energy?
A. Solar energy is the cleanest and most sustainable of all known energy sources. The sun emits radiation that provides us with a plentiful supply of energy. The sun powers natural cycles on earth like the wind, water flow and plant growth. But the sun is also such a reliable source of heat and light that we sometimes take it for granted. Generations have used glass and other materials and structures to capture and magnify the sun’s energy and these systems have gradually evolved to form the basis of mature techniques that are used today to harness solar energy.

Q. What is a solar thermal heating system?
A. A solar thermal heating system is a system designed to heat water using energy from the sun. The most common and cost efficient type of solar system installed in Ireland is used to heat your domestic hot water but a system can also be designed to contribute some heat  to your central heating (Though this will not suit ever situation).

Q. What is the difference between solar thermal and photovoltaic’s?
A. Both solar thermal, as well as photovoltaic’s, are systems which utilise the energy from the sun. Solar thermal systems generate heat (For hot water or space heating) with the radiation from the sun. A photovoltaic system uses the solar radiation to generate electricity. (See our information on Solar PV)

Q. Does solar thermal work in Ireland?
A. Yes. Even on cloudy and overcast days in summer and winter, solar thermal systems will supply heat to your water, delivering on average up to between 60% and 70% of your annual hot water requirements. During the winter your solar system will be preheating the water and during the summer months it will provide up to 80% - 100% of your hot water needs. There is a widely held opinion that Ireland does not have enough 'sun' to make solar systems worthwhile. In fact parts of Ireland have enough annual solar radiation levels equal to 60% of those experienced at the equator and the as much solar energy as central Europe.

Q. Will I get any benefit from my solar system in the winter?
A. Yes, studies and simulations have shown solar systems to provide between to 20% - 40% of hot water requirements during the months of November to February.

Q. How does a solar hot water heating system work?
A. A special liquid is circulated through the solar panel (which collects the solar energy) and transfers this heat energy to the liquid. The solar panels are designed to maximize the solar radiation absorption and minimize heat loss. This liquid is then pumped to the storage/hot water cylinder where it heats the water and leaves it ready for use.

Q. Why install a Solar Thermal System? (Advantages of a Solar Thermal System).
A. A solar thermal system provides free heat for your domestic hot water (DHW) and can also support space heating. By installing a Solar Thermal System you will save on heating costs, protect the environment due to reduced CO2 emissions (reduce your carbon footprint), you will improve the BER rating of your house and thus increase its value. There is also great comfort in knowing that there will be hot water available when you need it. You will also extend the life of your current heating system.


Q. Which are better, Evacuated Tube Solar Collectors or Flat Plate Solar Collectors?
A. Both types of Solar Collectors have different advantages as listed below. The type of Solar Panel you choose will depend on a number of factors including the orientation of your house, the space available on your roof, location in which the panels are to be installed and your own personnel preferences.

Advantages of Flat Plate Solar Collectors:

  • They can be integrated into the roof (Ideal for new builds).
  • Most people prefer how they look (i.e. Lower Profile with the appearance of large Velux Windows).
  • They are more robust.
  • They are not as expensive as Evacuated Tube Panels.
  • Lower maintenance (No need to replace tubes).


Advantages of Evacuated Tube Solar Collectors:

  • They are more efficient per square metre thus they may be preferential if you are limited on space (But Flat Panel versus Evacuated Tube Panel has very similar outputs i.e. Flat panels usually have a larger area).
  • They may work a little better in winter when the sun is at a lower angle.
  • They may work a little better if the house is badly orientated.

 

Q. How much will my solar thermal system save me?
A. On average, your solar thermal system will provide up to 100% of your hot water requirements during the non-winter months. During the winter months, the system will provide 20% to 40% of your hot water needs. This equates to an annual average of about 70% of your hot water heating costs. In a family of about five, this equates to about 350 to 500L of oil or 3200 to 4000 units of electricity.

Q. What is the payback time on the technology?
A. Payback periods vary, depending on a number of factors including the type of fuel displaced, the annual increase in cost of the fuel displaced, the amount of hot water you use and the initial cost of the solar system.
A typical payback time for a household of 5 people who normally use oil or gas to heat their hot water would be about 6 to 8 years or 4 to 5 years if they use electricity.

Q. Is a solar thermal system economical?
A. The economic efficiency of solar systems is widely calculated by comparing the one-time investment in the solar thermal installation to savings made in the reduced consumption of other energy sources like oil, gas or electricity. Rising prices for oil and gas make solar heating more and more attractive from day to day.

Q. How much does hot water usage within my home contribute towards my overall energy bill?
A. Most people significantly underestimate the amount of hot water they use. Baths, showers, hot water drawn from a tap and hot-fill washing machines and dishwashers can contribute to about 30% of your overall heating bill.

Q. How much will a solar hot water system cost me?
A. The cost of the system and installation will depend on a number of factors. The main one being the type of hot water system currently used in the property. Do you have a vented or unvented system or use a combination (combi) boiler? To utilize solar heating you need to have a solar compatible hot water cylinder installed. Unvented hot water cylinders are a little more expensive then vented systems. If you have a combi boiler supplying your hot water then it will need to be capable of accepting warmed water from the solar array. Another factor will be where the solar collectors and Cylinder will be located. And of course we need to consider how many people the system will cater for.

Q. Can I still use my boiler or electric immersion to heat my hot water?
A. Yes, these heat sources are still available and will be required to boost the temperature in the winter when there is not as much solar energy but will be rarely used in the summer months.

Q. Are grants available for installing Solar panels?
A. Currently there are grants available for existing dwellings from Sustainable Energy Ireland (SEI). Please refer to our webpage ‘Grants & Incentives’.

Q. I have more than one house - Can I apply for a grant on more than one property?
A. As long as you are the owner of each house, you can apply for a grant in respect of each. You will have to make a separate application for each house. Please refer to our webpage ‘Grants & Incentives’.

Q. Is there an expiry date for the SEI grant approval?
A. Yes, 6 months from your grant approval date.

Q. Do I need planning permission?
A. Planning exemptions are in place which means that planning permission is not required for the vast majority of installations.

Q. Is my property suitable?
A. Solar panels work best with an orientation between south east and south west. They will still work outside of this range but with reduced output. Ideally the roof should also be free from shade. Solar panels are available for all most types of roofs. If required solar panels can also be mounted on frames on flat roofs or on the ground.

Q. What is the life expectancy of the Solar Panels/are there any guarantees?
A. All our solar panels come with a manufacturer’s warranty of between 5 and 10 years (depending on model chosen); however, the expected life span of a good quality solar panel can be anything from 20 to 25 years. Poorer quality cheaper solar panels will be less.

Q. Are the solar panels and storage tank certified by a quality label and CE compliance label?
A. Yes.


Q. Is the system protected against overheating, freezing and excessive pressure?
A. Yes.

Q. What size of system do I need?
A. Systems sizes are determined based on a number of variables such as your hot water demand, the orientation of the panels and the cylinder capacity. We will design and select the ideal system for your particular circumstances.

Q. How are hot water requirements calculated and how is the solar water system sized?
A. The hot water requirements are calculated by taking into account the number of people living in the house. Each person living in the house is calculated at approximately 50 litres per day (average usage). The solar system is then sized to heat the chosen cylinder, taking into account the climate conditions and the orientation & pitch of the roof.

Q. Will I need a new hot water cylinder?
A. This will depend on what type of cylinder you currently have, but we can check this at the time of initial survey. In most cases it makes more sense from a financial and performance point of view to install a new solar cylinder.

Q. How big does my hot press need to be for the new cylinder?
A. Solar cylinders tend to be larger than your standard hot water cylinder. We can check the size of your hot press during the survey. We supply cylinders of various different shapes and sizes so we can select one to suit your needs.


Q. Are solar hot water systems user friendly?
A. Yes. Our solar systems come with a solar controller which will monitor the temperature at the solar panels and the temperature in the hot water cylinder. This will automatically turn the solar pump on and off as need be thus controlling your solar system. The system is fully automatic.

Q. Can a solar system be used in conjunction with my existing heating system?
A. More than likely yes, we can verify this at the time of site survey. We can supply you with a dual or triple coil solar cylinder so you can heat your water via your existing heating system/s as well as with the solar collectors.

Q. Can I heat my swimming pool using solar panels?
A. Yes. In fact heating a swimming pool with solar panels can provide a very efficient use of solar panels.


Q. Can hail cause any damage to the collectors?
A. All our solar panels are manufactured from hail resistant glass.

Q. What kind of maintenance does a solar thermal installation require?
A. A solar thermal system requires very little in terms of maintenance. Ideally you should have the system checked once every two years and fully serviced every four years.

Q. What kind of fluid runs through a solar thermal system?
A. In a solar thermal system a ‘food grade’ heat transfer liquid with antifreeze properties (Tyfocor or Glycol) is used.

Q. Do you supply, install and commission the solar system from start to finish?
A. Yes we offer a full turnkey service from design to commissioning including maintenance / servicing (if required).

Q. What does the installation involve?
A. In the majority of homes, installation will be done in less than 2 to 3 days. The installation process involves fitting the solar panels to your roof, connecting the pipes to the solar cylinder and then commissioning of the system. For more information see our webpage on ‘Solar Water Heating’.

Q. Are the solar collectors noticeable on the roof?
A. Flat panels are normally less noticeable than the evacuated tube type. Roof integrated flat panels (which look similar to large velux windows) have a lower profile than the roof mounted type but regardless of which type you choose they should blend into the roof design quite well.
If you are concerned about how they might look we would be happy to direct you to one of our installations in your area so you can see for yourself or alternatively we can email photos to you of some installations.