Solar Water Heating

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					Waterford Energy Bureau
Renewable Energy Fact Sheet No.5 (A)
                                             Solar Energy

                                Brief Description
           Solar water heater is an efficient and                                                         A back up heater (gas/oil boiler,
           reliable technology that converts sunlight                                                      immersion heater, heat pump),
           into heat to produce hot water. A solar                                                         which will bring the hot water to
           water heater can reduce your hot water and                                                      temperature required when there is
           heating bill by between 40-70%.                                                                 not enough sunlight to do so
           In Ireland a horizontal surface of 1m2                                                          (mostly in winter).
           receives an average of between 1,000kWh                                                 In Ireland, solar collectors alone cannot
           and 1,200kWh of solar energy per year                                                   provide all the hot water for a household’s
           (the equivalent of 120                                                                  needs throughout the year. They are
           litres of oil).     Both                                                                normally installed in conjunction with a
           direct sunlight (40%)                                                                   conventional heating system.
           and indirect sunlight                                                                              Types of Solar water heating
           (60%) provide this energy. So even when
                                                                                                   Two main types of solar collectors, both
           the sky is over cast you can’t see the sun,
                                                                                                   available on the Irish market include:
           its radiation (sunlight) is available at
           ground level and can be converted into                                                       Flat plate collectors, with a
           useful heat by solar water heater. On a                                                         selective absorber, are well suited
           bright day, any surface standing in the sun                                                     for hot water production and low
           will receive about 1,000 watts of solar                                                         temperature heating. (Typical
           radiation (a power equivalent to that of 10                                                     efficiency of 40%)
           strong bulbs).                                                                               Evacuated tube collectors that are
                                                                                                           more efficient with higher water
                         Solar thermal technology                                                          temperature and provide solar
           This type of system typically uses a                                                            water heating when solar radiation
           transpired collector, consisting of a thin,                                                     is less intense. (Typical efficiency
           black metal panel mounted on a south-                                                           of 60%).
           facing wall to absorb the suns heat. Active                                                         Uses of Solar water heating
           space heating linked to under floor heating
           projects here in Ireland.                                                               Hot water from the solar water heating
                A solar collector which absorbs                                                   system can be used for
                   solar radiation (sunlight) and                                                       Central heating
                   changes it into heat;                                                                Swimming pools
                A pump which transfers the heat                                                        Domestic hot water
                   from the collector to hot water in a                                                                 Installation Costs
                   storage tank;
                The         storage                                                               The table below gives you an idea of the
                   tank                                                                            size and cost of an evacuated tube solar
                   accumulates hot                                                                 water heater for domestic hot water,
                   water produced                                                                  according to the number of people in your
                   by solar energy                                                                 household:
                   so that it can be
                   used when it is

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    Evacuated tube –solar water heating                                                             Solar Water Heating
     installation for domestic hot water                                                A correctly sized solar water heating
Number            Area of            Volume            Indicative                       system will cover 50 to 60% of your hot
of people         solar              of       the      initial                          water heating requirement with free solar
in    the         collectors         solar hot         investment
house             (*                 water             (**)
                                                                                        energy. Solar water heaters comprise of a
                  evacuated          tanks                                              solar collector, pump, controller and a hot
                  tube)              (litres)                                           water storage cylinder
2-3               2-4m2              100/200           €3500/5500                                          Savings
                                                                                        Your annual energy savings will depend
4-5               4-6m2              200/300           €5500/€7000
                                                                                        on the kind of energy you are replacing
6-7               6-8m2              300/400           €700/€9000                       and the evolution of its price. Apart from
                                                                                        saving up to 60% annually, your savings
                                                                                        will increase as           the   price   of
(*) Area for flat plate collectors. The
                                                                                        oil/gas/electricity increases over the next
equivalent area for evacuated tube
                                                                                        20 years.
collectors will be smaller as they have a
                                                                                        About 65% of the energy consumption in
higher efficiency.
                                                                                        our house area for space heating and
(**) Price of a complete solar package
                                                                                        another 15% are for hot water production
(collectors storage tank, controller, pump,
                                                                                        and 20% losses through conventional
hydraulic components etc.) excluding
                                                                                        boiler inefficiencies.
VAT and installation. Installation should
                                                                                        For most buildings heating bills can be
require two or three days for a skilled
                                                                                        reduced by 20% at negligible capital cost
                                                                                        by applying
The optimal inclination for your solar
                                                                                        passive solar
collectors is 20 degrees – 50 degrees. But
they can be titled from 30 degrees – 60
degrees without significant loss of
                                                                                        larger savings
performance. Collector panels are most
                                                                                        can          be
productive when facing south. However
                                                                                        achieved if a
they can be oriented between southeast
and southwest with out significant loss of
                                                                                        comprehensive low energy design strategy
                                                                                        is adopted. Passive solar heating relies on
 Guide to installing Solar Water Heating
                                                                                        collection, conservation, storage and
Adequate space should be left to install the
                                                                                        distribution. Solar energy can be utilised
solar storage cylinder (200-300 litres) in a
                                                                                        in different ways.
hot press or boiler room.
The optimum area of collector, which
might be installed in a dwelling, depends
on the hot water demand. It is generally                                                         Waterford Energy Bureau
held that 3-5m2 of flat plate collectors                                                               Civic Offices
might be right for a family of up to 4                                                                   Tankfield
persons; for 5-6 people 4-6 m2 might be                                                                  Tramore
the     optimum.      The     corresponding
                                                                                                      Co. Waterford
evacuated tube collector absorber area
                                                                                              Phone No: 051-395530/395531
may be reduced to two thirds of the
equivalent flat plate collector.                                                                   Fax No: 051-395520
 It is generally expected that a well                                                   
designed system will provide the majority
(typically 80%) of a family’s hot water
requirements during the summer months
and make a useful contribution during the
rest of the year. This means that up to 60%
of the bill for heating hot water can be
saved in a typical year.

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