Solar FP Projects

This is a compilation of projects that I and my compatriots are working on at Solar FP. We try to pick projects which are novel but still doable by a skilled individual. Some projects involve new ideas we came up with at Solar FP. Other projects are just our attempt to duplicate or improve upon other ideas we have seen which were interesting.

Feel free to tell us about projects you want to see. We love new ideas and will do what we can to shed light (no put intended) upon the technologies which interest you.

1. Solar Greenhouse for Electrical Power Generation - This project involves the purchase of a commonly available small greenhouse (10' x 12' or 120 ft²) that we then convert to harness a convection current. The theory is simple and has been applied on a large scale before. As the air in the green house heats up, it pressurizes the green house or gets lighter if the pressure can escape. By placing an insulated chimney at the apex of the greenhouse. The heated air wants to escape out the chimney. To create a cycle, one or more small opening are created at the base of the greenhouse. Thus the air escaping out the chimney draws cool air into the greenhouse. This air is then heated and escapes and the cycle continues. This current of air is basically a locally created wind than we can use to spin small turbines. The point of this experiment is to determine exactly how effective this can be on a small scale. The area of the greenhouse is approximately 13 m² This means on average it is receiving 13,000 watts of energy from the sun in a typical US state. However, the temperature difference between the cold and hot side of our "engine" is very small. Probably only 8 deg K. Thus, the Carnot equation would limit or maximum power generation at ( 1 - 273 / 281 ) * 13,000 or 370 watts. This is approximately 1/2 horsepower. But that assumed our system was as efficient as it could be. In reality, there will be many other losses in our system. I think we will be lucky to get 100 watts out of this device. The up side is that we get a usable greenhouse out of it. It all goes well, we should end up with data indicating what size of greenhouse would be required to say power a typical household.

2. A simple off-grid one sun photo-voltaic system. - Which is a fancy way of saying that I want to put some lights in my Barn but don't want to run AC wires out there. This might be typical of an application worth doing for reasons other than cheaper power generation. I purchased a 45 watt panel set off of EBay, tossed out the controller, which was basically useless. Experimented with some different charge controllers and came up with a good battery charger that can power some low power lighting and a small (300 watt) psuedo sine wave generator for the occasional AC requirement in the barn.

3. A simple pointed trough system hot water/oil system. This is really the beginnings of a more complicated hybrid system for electrical generation. In this phase I just  use some 6" PVC pipe cut in 3rds, lengthwise to make semi-parabolic reflectors. I am using reflective film from greenpowerscience.com initially, but will likely play with different reflective coatings later. The trough is oriented north to south to accommodate seasonal changes in sun angle. The array is actively pointed east to west to track the sun. Parabolic mirror concentration is used to achieve high fluid temperatures while minimizing radiation from the hot tubes. Water then eventually oil is pumped through tubes that are located at the focal point of the reflectors to an insulated storage tank. The scope of this project is to simply create the collectors, the pointing mechanism, and the storage tank. Later projects will incorporate water heating exchangers and electrical power generation like stirling engines or TEG devices.

4. A hybrid thermal-electric high temperature system. This is the most complicated of our projects to date and will likely take a while to finish. The goal here is to use some pointed thermal troughs, heat some oil to around 200 deg C, Store it in a well insulated reservoir, and then use that heat for space heating, domestic water heating, and finally for generating electrical power with TEG devices. TEG devices are less expensive than PV panels per watt rating, but require a lot more support mechanism to realize that watt rating. This system puts us to the test to see if we can come up with a reliable way of getting electrical power from a high temperature heat reservoir. The higher temperature is necessary for TEG efficiency and for adequate heat for water baseboard space heating. 200 deg C is hot enough to bake a cake, so there are definitely some safety concerns with this project. If it works, though, this system can address a main criticism of solar power. That is, this type of system can generate power long after the sun goes down. Theoretically it could produce power for many days based upon the capacity of the oil reservoir and insulation of the reservoir. This also means that 100 watts of TEC generation is worth 400 watts of PV generation. Why, because the PVs can only make the 400 watts of power when the sun is shinning... say for 6 hours per day. The TEC system can make power 24 hours per day and the storage price for hot oil is many times cheaper than batteries or other electrical means of storing energy.