Steam Turbine/Heat Engines
The steam turbine or heat engine is very important in this system. It converts heat to mechanical energy and is the step in the system that has the lowest efficiency.
For small steam turbines (3000 watts) operating at 200-300C, 20% thermal efficiency is really the best that can ever be hoped for. This 20% efficiency means that the turbine will convert 1000 watts of heat into only 200 watts of mechanical power. Large turbines running at higher temperatures can achieve efficiencies well over 40%.
From my initial research I have decided to start testing using a Tesla turbine. It is one of the easiest turbines to built yourself and is very efficient and light weight. I am working with Ryerson University in Toronto Canada to build a precision CNC machined Tesla steam turbine. I will also be building another Tesla turbine using only simple hand tools.
A Tesla turbine uses a series of flat disks that have small gaps between them. Steam flows at high pressure tangentially into the disks and the drag between the disk surfaces and steam causes the turbine to rotate. The steam spirals to the centre of the disks where it exits the turbine housing. This turbine is so easy to build because it has only flat disks and no complex shaped turbine fins.
Homemade Tesla turbine
I will start by building the turbine using sheet metal and sheet metal sheers. 2 low drag Rollerblade bearings will be used to support a metal shaft. The disks will be mounted on a drill and their edges will be sanded to ensure they are perfectly round. JB weld will be used to attach the disk and spacers to the shaft. This Turbine will allow me to start testing before the machined turbine arrives and will allow me to compare the cheap homemade turbine to the machined version. I am hoping to develop this homemade Tesla turbine to be built in developing countries out of available recycled materials so solar thermal power can be used to pump water and create electricity.
I have also thought a car Turbo charger turbine could be used as a small steam turbine. I am always looking for existing used parts that can be used in the solar thermal car.