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Solar Thermal - Solar Water Heating Collectors

Solar Thermal - Solar Water Heating Collectors

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Solar Thermal - Solar Water Heating Collectors

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  1. Solar Thermal - Solar Water Heating Collectors Solar energy can be captured by solar panels. These panels absorb the energy from the sun and transfer it to heat water. Solar Power Solar water heating systems are the most popular form of solar energy used in the UK. The system is connected to the hot water system. Solar water heating systems can provide over half of a household's hot water requirements over the year. There are 2 types of solar water heating collector: flat plate and evacuated tubes.

  2. Solar Electricity - Photovoltaic (PV) Panels Solar energy can be captured by solar panels. Photovoltaic (PV) or solar electric panels transform the solar radiation directly into electricity. PV or solar electric offer the ability to generate electricity in a clean, quiet and renewable way. The variety of applications for solar electric are numerous. Photovoltaic (PV) cells are used in simple applications e.g. calculators and watches and also for domestic and larger applications. Large PV systems can be integrated into buildings to generate electricity for export to the national grid.

  3. Biomass - Wood fuel/pellets burning stoves/boilers In order not to increase the amount of carbon dioxide in the atmosphere it is important that the wood burned as a fuel comes from sustainable sources. This means that as trees are felled to be use as a fuel, more trees should be planted. That way, the carbon released during the combustion of the wood is reabsorbed by the new trees growing and the process is carbon neutral. Wood can be used as logs, wood chip and wood pellets in wood/pellet burning stoves or wood chip/pellet boilers for space and water heating.

  4. Heat from the Sun - Ground Source Heat Pumps When the sun shines on the ground its heat energy is absorbed. Ground source heat pumps extract this energy, to use for space heating. So strictly speaking, the energy source that is used for ground source heat pumps is the sun and not the heat from the earth.

  5. Wind Power - Wind Turbines The power of wind has been used for many years to produce mechanical power for milling grain and pumping water. In recent times wind turbine technology harness wind to generate electricity. The electricity is then exported either to the grid for use locally or to power a stand alone application. This renewable source of energy has great potential in both onshore and offshore wind farms. Wind power is one of the cleanest and safest of all the renewable commercial methods of generating electricity.

  6. Hydropower - Water Wheels The energy potential of moving water has been harnessed for thousands of years, originally using water wheels to drive mills and machinery. Hydropower currently produces 2% of the UK electricity needs. Whilst most of this comes from large dam projects installed many years ago, there is still an untapped small hydropower potential in certain parts of the UK.

  7. PRODUZIONE DI IDROGENO • processi derivanti dall’ industria petrolchimica e quindi non da fonti rinnovabili, coprono oltre il 90% della produzione mondiale di idrogeno e sono • Steam methane reforming, • massificazione del carbone, • ossidazione parziale di idrocarburi a basso punto di ebollizione, • elettrolisi dell’ acqua • produzione da metanolo ed ammoniaca

  8. MASSIFICAZIONE DEL CARBONE Il processo piu’ comune è quello del cosiddetto gas d’ acqua, cioè la reazione endotermica tra coke e vapore a 100 °C C + H2O  CO + H2 H° = 31,380 kcal Il calore necessario alla reazione endotermica puo’ essere fornito alternandolo con la reazione esotermica C + O2  CO2 H° = - 94,05 kcal L’ ossido di carbonio viene poi trasformato in idrogeno a 500 °C facendolo passare insieme ad un eccesso di vapor acqueo su un letto di catalisi composto di ossido di ferro e di cromo CO + H2O  CO2 + H2 H° = - 9,83 kcal

  9. ELETTROLISI L’elettrolisi copre attualmente un mercato di nicchia (circa il 4% della produzione mondiale) per soddisfare fabbisogni di H2 ad alta purezza che, pur avendo costi elevati è l’unico processo che permetta la produzione di idrogeno a partire dall’acqua utilizzando energia elettrica. Gli impianti industriali piu’ importanti sono stati costruiti in quelle aree in cui il basso costo dell’ energia elettrica lo giustifica da un punto di vista economico ( Egitto, Peru’, India). Attualmente le celle elettrolitiche sono essenzialmente costituite da due elettrodi separati da una diaframma impermeabile ai gas ed in cui il 20,30% di idrossido di potassio è disciolto nella soluzione acquosa per incrementarne la conduttività. La temperatura a cui avviene l’ elettrolisi è di circa 85 °C. L’ ossigeno viene prodotto all’ anodo e l’ idrogeno al catodo secondo le seguenti semi reazioni : 2OH-  H2O + 0.5 O2 + 2 e- anodo 2 H2O+2e-  H2 + 2 OH- catodo Il bilancio della reazione è il seguente H2O  H2 + 1/2O2 L’ energia consumata per m3 di idrogeno e 0.5 m3 di ossigeno è intorno ai 5kWh

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