HYBRID PV/T SOLAR WATER HEATERS. Soteris Kalogirou Higher Technical Institute Nicosia-Cyprus. Contents. Solar energy in Cyprus Solar water heating PV applications Hybrid PV/T systems PV/T system modeling Conclusions. Island of Cyprus.
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HYBRID PV/T SOLAR WATER HEATERS Soteris Kalogirou Higher Technical Institute Nicosia-Cyprus Intensive program: ICT tools in PV-systems Engineering
Contents • Solar energy in Cyprus • Solar water heating • PV applications • Hybrid PV/T systems • PV/T system modeling • Conclusions Intensive program: ICT tools in PV-systems Engineering
Island of Cyprus • Cyprus is the third largest island in the Mediterranean at 35° north latitude. • Area= 9,251 km2. • Population: about 750,000. • Member EU as from 1 May 2004. Intensive program: ICT tools in PV-systems Engineering
Cyprus energy scene • Cyprus has no natural oil resources and relies entirely on imported fuel for its energy demands. • The only natural energy resource available is solar energy. • The climatic conditions of Cyprus are predominantly very sunny. • Daily average solar radiation of about 5.4 kWh/m2 on a horizontal surface. Intensive program: ICT tools in PV-systems Engineering
SOLAR WATER HEATING • At present solar energy covers about 4.5% of the total annual energy requirements. • Furthermore, it contributes to a reduction in the atmospheric pollution by approximately 260,000 tons of CO2per year. Intensive program: ICT tools in PV-systems Engineering
Typical solar water heaters in Cyprus • These are of the thermosyphon type and consists of: • Two flat-plate solar collectors having an absorber area between 3 to 4 m2, • A storage tank with capacity between 150 to 180 litres, • A cold water storage tank; and • An auxiliary 3 kW electric immersion heater. • In buildings which are equipped with oil fired central heating systems the boiler is used as auxiliary through a heat exchanger fitted in the storage tank of the unit. Intensive program: ICT tools in PV-systems Engineering
Current situation • 93% of houses • 50% of hotels • The estimated park of solar collectors in working order is 560,000 m2 • Total number of units = 190,000 • Corresponds to 3.7 inhabitants per unit • World Record • Second: Greece • Third: Israel Equipped with solar water heaters Intensive program: ICT tools in PV-systems Engineering
Systems installed • 96% of the collector area installed up today (540,000 m2) are installed in houses and flats. • In the tourist industry, it is estimated that: • 44% of the existing hotels; and • 80% of the existing hotel apartments are equipped with solar-assisted water heating systems. The contribution of solar energy to the total energy consumption in the hotel industry is 2%. Intensive program: ICT tools in PV-systems Engineering
Collector performance prediction • Simulation studies of this kind of system were conducted with TRNSYS and the typical meteorological year (TMY) values for Nicosia-Cyprus. • Results: • 80% of the hot water needs are covered with solar energy (solar contribution). • No auxiliary needs for four months. • Life Cycle Savings = £427 (725 Euro). Intensive program: ICT tools in PV-systems Engineering
PV Applications • PV can be applied in any environment • Snow • Sea • Desert • Space • Some of the most typical are shown in the next slides Intensive program: ICT tools in PV-systems Engineering
PV in snow Intensive program: ICT tools in PV-systems Engineering
PV in Alaska Intensive program: ICT tools in PV-systems Engineering
PV in sea Intensive program: ICT tools in PV-systems Engineering
PV in desert #1 Intensive program: ICT tools in PV-systems Engineering
PV in desert #2 Intensive program: ICT tools in PV-systems Engineering
PV in space Intensive program: ICT tools in PV-systems Engineering
PV on Mars Intensive program: ICT tools in PV-systems Engineering
PV Applications • Typical applications include: • Solar roofs • Transmission stations • Emergency lighting • Shading devices • Water pumping • And many other….. Intensive program: ICT tools in PV-systems Engineering
Solar roof Intensive program: ICT tools in PV-systems Engineering
Water pumping Intensive program: ICT tools in PV-systems Engineering
PV Shading-1 Intensive program: ICT tools in PV-systems Engineering
PV shading-2 Intensive program: ICT tools in PV-systems Engineering
Car park shading Intensive program: ICT tools in PV-systems Engineering
PV tracking Intensive program: ICT tools in PV-systems Engineering
Concentrating PV Intensive program: ICT tools in PV-systems Engineering
PV in Cyprus • Despite the high penetration of SWH no other application has grown in Cyprus. • Very few applications of PV are available • Powering transmission station in mountain peaks (no grid available) • House applications • Water pumping • Telephone booths lighting • One factory recently start operation Intensive program: ICT tools in PV-systems Engineering
Hybrid PV/T Systems PV characteristics Methods of extracting thermal energy Air and water systems Intensive program: ICT tools in PV-systems Engineering
Solar radiation 100% PV panel Electricity 15% Waste 85% Heat mostly PV Characteristics If waste heat is not removed PV can reach temperatures of 40°C above ambient Intensive program: ICT tools in PV-systems Engineering
Why should a solar device produce both electricity and heat • Because user needs both • Easy to cell electricity • Hot water is also required-save conventional energy • Use one system instead of two • Different systems: • One system for electricity (PV) • One system for solar thermal heat Intensive program: ICT tools in PV-systems Engineering
Why we should have a combined system? • There is not enough roof space • PV/T is cheaper • PV/T is nicer (one system of same appearance) • PV/T system is more efficient • It would be difficult to introduce PVs in countries with good penetration of SWHs A system producing electricity and hot water has better chances of success. Intensive program: ICT tools in PV-systems Engineering
Temperature increase of PV modules • The temperature of PV modules increases by the absorbed solar radiation that is not converted into electricity causing a decrease in their efficiency. • For monocrystalline silicon solar cells efficiency decreases by about 0.45% for every degree rise in temperature. • For amorphous silicon cells the effect is less pronounced, with a decrease of about 0.25% per degree rise in temperature. • This undesirable effect can be partially avoided by a proper heat extraction with a fluid circulation. • In hybrid Photovoltaic/Thermal (PV/T) solar systems the reduction of PV module temperature can be combined with a useful fluid heating. Intensive program: ICT tools in PV-systems Engineering
PV Cooling • PV cooling is considered necessary to keep electrical efficiency at a satisfactory level. • Natural or forced air circulation are simple and low cost methods to remove heat from PV modules. • they are less effective if ambient air temperature is over 20°C. • To overcome this effect the heat can be extracted by circulating water through a heat exchanger that is mounted at the rear surface of the PV module. Intensive program: ICT tools in PV-systems Engineering
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