Power for this system begins with the sun strength and size of the solar thermal mirror. The incoming power from the sun will have to go through many steps, each with their own efficiencies, before the power can be used to propel the car.
Incoming power for the car can be calculated by assuming the mirror is 2 meters wide and 8 meters long. This results in 16 square meters. On a strong sunny day at noon the incoming sun power is approximately 1000 watts per square meter. This results in the figure of 16,000 watts of power as our best case inputed power.
In the early designs, 3 different power calculations were done using an excel spreadsheet. The power was calculated by taking the input power and multiplying it by the efficiency figures for each stage. When the final figures for the power to be transfered to the wheels was calculated, we used the power storage capacity and the drag of the vehicle to calculate the distance the car can travel on each charge and each day (assuming 6 hours of full sun 1000w/m^2).
The best case scenario was calculated with all efficiencies at 100% and the efficiency of the steam turbine set at 20%. A 20% efficiency for such a small turbine is very good. We also used a drag value to maintain 90km/h as 7.5hp, which is also a best possible case aerodynamics scenario, and was taken from an old Corvette. The solar thermal car will have a significantly higher drag. So the best case scenario gives us a value of over 200km of travel per day. We already thought that we would be travelling less than 100km per day using only solar power so this number works well for us. We want to travel slowly to enjoy our trip.
The middle case scenario is much more realistic with a drag of 10.5hp at 90km/h which is approximatly the darg of our car the Mazda protege. I am hoping the Aerodynamic system on the trailer will greatly reduce the trailer drag so the car and trailer drag will be close or less than the drag of just the car. The middle case is still very optimistic with perfect mirror and heat absorption and no heat loss.
The worst case was calculated to give a more realistic lower base number. All numbers highlighted in red are the exaggerated worst case. I assumed a 50% efficiency from sunlight to oil, which is very low and not very probable as the final efficiency. We maintained better efficiencies using primitive aluminium foil and plywood test units (efficiency test). As such, it is logical to assume that by the time the car is built, the efficiencies will be greatly increased with the introduction of stale air or vacuum insulation. Next we assumed a 25% radiation heat loss. This was calculated at 200C using the worse case black body radiating into an absolute zero environment. The last worst case value is the drag which I increased to, 25hp to maintain 90km/h, which is similar to that of a truck. This figure gives a travelling distance of only 32km per day and makes travelling around the world in less than 50 years very unlikely. During design and testing I will be working very hard to get more heat into the oil and reduce the drag of the vehicle as much as possible. If we have this little power to work with we will be travelling much slower (less than 60km/h) in order to get the greatest distance from our power.