Water Loop System
The water loop system takes the heat from the oil loop through the heat exchanger and converts it into high pressure steam to power the steam turbine. For the solar thermal car a closed loop system is required that condenses the steam from the turbine and reuses it. This is required because a large water tank would be too heavy on the car. For stationary systems where a large water source is present an open water loop system can be used that just vents the turbine exhaust steam. This results in a cheaper and less complex system.
The closed water loop has a pressurized and non pressurized side. The section between the water feed pump and the steam Turbine is under high pressure. After the steam turbine there is a drop in pressure through the turbine and the water is condensed reducing the pressure back to atmospheric. The feed water pump must then pump the low pressure water into the high pressure boiler. The heat from the oil then turns the water to steam to create the very high pressures for the steam Turbine.
My preliminary water loop design consists of 5 major sub systems. The numbers I am using match the ones in the picture below.
1 First a high pressure pump forces water through the feed water heater when the water level in the boiler is low (see boiler feed pump control). The feed water heater uses the hot turbine exhaust to pre heat the water entering the boil in a small double walled heat exchanger to conserve the heat in the system and increase efficiency.
2 The Heat exchanger. The water or steam now enters the large double walled heat exchanger boiler. Hot oil flows around the central water tube to heat it and change it to high pressure steam.
4 Now the turbine exhaust is used to heat up the boiler feed water in the pre heater and is cooled down in this process to prepare for condensing.
5 The Condenser. Will be used to turn the steam back into water so that it can flow back into the water tank and be pump into the pre heater to start the cycle over again. In order to increase efficiency I am looking into using lower temperature heat engines to condense the steam and create extra power for the system.