for calculating power of sunlight its said to have roughly 1000 watts per m2 of available power for solar applications.
https://core.ac.uk/download/pdf/82014726.pdf solar hot water heator
hot water tanks installed in/on the roof with black tubing or painted black garden hose on the roof can easily collect the rays of the sun. could use a heat exchanger and cover with clear plastic on a steep slope with solar pump if you plan on using it during winter on sunny days for underfloor heating or for driveway.
solar collectors can be built from aluminum flashing for foundations easily.
aluminum can solar collectors can be made easily too even without a glass top for non winter applications, have thought about using an old car before too. great for hot water / air in summer winter depending on the build.
solar waterer system for cattle
https://www.ebay.ca/itm/401436481978 took a month to ship, eventually did come but i was unable to leave feedback for it on ebay. puts out about 3.5v and 0.6 amps – 2 watts on a overcast day not sure it would see a full 10 watts of power unless a concentrator was used. (if you get one of these wash it off good(mostly the sides of it where the plastic layers meet), not sure if it was something i did but i had chemical taste in my mouth afterwards)
http://www.alternative-energy-news.info/floating-solar-panels/ if they were to use peltier coolers as heat converters to make more power it could get up to around 35% efficiency
25% efficient 75% heat waste
2% gain per 10 deg cooling
5%-10% TEC peltier conversion
can find 2 of these for 1000 dollars on some listings