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
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