Catharsis

 We're investigating improving our home heating situation. Electric heat pumps seem to be the way to go. They're rated using SEER (cooling efficiency) and HSPF (heating efficiency). You'd think efficiency would be dimensionless, or maybe in per cent , to move some significant digits into the integer part of the number. Consider my final grade in high school social studies. 67% means I understood two-thirds of the material, or 0.67 as a decimal number.  But no!  Heat pumps use electricity. The only unit anyone knows for electrical energy is kilowatt-hour. Heat pumps pump heat. The only unit anyone knows for heating and cooling is BTU. So both SER and HSPF are in units of BTU/W-h. watt-hour instead of kilowatt-hour, to get rid of those pesky digits to the right of the decimal point. A good heat pump has an HSPF of about 15. That has no intuitive value. Convert from BTU/W-h to just efficiency by multiplying by 0.29307 BTUs per watt-hour. An HSPF of 15 has an efficiency of arou

W e use an oil-fired boiler feeding 180°F water to hydronic baseboards to heat the house. It also supplies domestic hot water ( very  hot water!) for washing dishes and people. I think the boiler has a small, maybe 5 gallon, reservoir, but it might only have a buffer of hot water in the heating coil. I looked at our fuel bills. Taking the timeline of fuel deliveries and dividing the quantity delivered by the number of days since the last delivery gives a rough idea of the consumption per day preceding that fill up. The suppliers like to fill it up, so at the time of every dot in this graph, we have a full tank. The black dots are the total consumption per day estimates, calculated as the amount needed to refill the tank (i.e. what was consumed), divided by the number of days since the last full tank. The dots fall into two bands, roughly - below and above 5 liters per day. We can average those below 5 l/d, assuming that's when it's only making hot water, not heating the house.

 One aspect that Danielle is neglecting in her hatred of renewable energy, and I'm only unconsciously aware of recently: there's peak load sure, but equally important in designing power systems, especially storage, is minimum load. Storage doesn't have to let us keep the status quo. Minimum load is below base load, it's the load that we really don't want unserviced. That's what storage has to provide. For everything else, the sun will come up, it'll get windy, or we can do without.  Let's just consider residential. In your house, minimum load is likely the fridge and freezer, and not much else. When things are dire, you won't be ironing the pillow cases. A little example: my fridge consumes an average of about 70 watts. When the compressor starts up, it uses around 1000 watts. But that's only for a minute or less. The compressor idles and the defrosting fan runs A LOT. These use about 110 watts. The light uses 40 watts. You can see when I had th