I remember the 1980 Carter energy scam. I worked for a custom home builder who put a hundred 55 gallon drums all plumbed in series into the sub basements of his million dollar homes. The drums were backf-filled with crushed stone and hooked up to passive solar hot water heaters on the mansion roofs. The idea was to store the heated water in the gravel bed barrels which then used it to heat the marble floors with heat exchangers in the wet bed tile bed.
It worked pretty well, but half the home building price was claimed under that program. Insane theft of taxpayer money.