Nadia Menouar, Lujain Al Momen, Noor Al Sharif
Dharan Ahliyya School, Dhahran , Saudi Arabia
Humans must resort more to renewable energies to minimize the effects of global warming. This research aims at building a hybrid electricity plant between a geothermal plant and an OTEC (Ocean Thermal Energy Conversion) plant. If NH3 could expand immensely because of geothermal heat, then enough electricity could be produced while making use of the drop in the NH3 gas temperature to regulate the temperature of a greenhouse instead of traditional cooling systems.
Since Ammonia has a low boiling point of -33,3 °C and a high coefficient of expansion {one cubic ft of NH3 liquid at 15°C expands to 850 cubic ft of gas}. That makes it able to turn a turbine with a delta T as low as 20°C.
Therefore, drilling a well of 2 km in depth with a gradient of 3°C/ 100m should be able to give enough heat to obtain a delta T of 60°C, knowing that water will be used only as a heat conductor. By making it a closed cycle, the NH3 gas drop in temperature will be used to regulate the temperature of a greenhouse. A miniature turbine engine was built and exposed to Ammonia vapor at a 50°C. The failure of that experiment emphasized that pressure will be needed in the turbine engine. Using the temperature drop as a variable, the plant`s efficiency computed was 10.39 %, a value much higher than the 4% obtained in OTEC plants. In conclusion, this research indicates that this plant promises a salubrious energy source.