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bjelkeman-again • today at 7:44 AM • 2 replies • view on HN

We have a wooden house from 1909, insulated, but not to modern standards and many windows. The heating and hot water is provided via a 10 kW (out) modern heat pump with a 100 meter borehole into the ground. This is a fairly standard installation in Sweden. It provides all the heat needed, except for extremely cold days (-20c or lower) when a 7 kW immersion heater can provide support. This is not needed more than a few days a year where we are.

We have added a small solar installation (7kWp) and a battery pack (18kWh). It provides 90% of power needed in the summer and allows for decent peak shaving in the winter, to lower network costs.

Additionally we are Co-owners in a windpower cooperative that provides more than our share of electricity into the network. So we are essentially operating our home on wind and solar, as well as powering the electric car.


Replies

throwaway2037 • today at 12:17 PM

    > 100 meter borehole into the ground
I have heard from a couple of different Swedes talking about when this was installed in their childhood/high school years. It must be reasonably common at this point in Sweden. Are there special machines that pull up to your home and bore a deep hole? That seems like very specialised work for the average contractor! Also, does the gov't offer subsidies from this (presumably) expensive home improvement?
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namibj • today at 11:03 AM

A big problem towards full electrification are those resistive extra heaters, due to their correlation across entire cities and correlation with extremely poor solar yields.

Unless there's a particular good reason to it's actually not too bad of an idea (with a hot water radiator loop in the home at least) to keep a fuel burning radiator loop heater around and just valve it off to not interfere on normal days. Especially if the heat pump is air source (which the mentioned swedish one isn't).

It's not that I'm against full electrification, but peak cold spell heating in excess of the heat pump capacity is among the last things we ought to "electrify by force."

We'd have massive summer overcapacity at the point where we can generally afford to "just do that". And chances are that it'd not be a resistive heater but a heat pump freezing a pool worth of water to cap the cold side temperature at just under 0C, or something the like, just because of how grid intensive the correlated load of those resistive heaters is.

It might even be cheaper to use synthetic fuel produced in summer than to 100% electrify that cold spell heating capacity. Carbon capture is expensive but there are options from e.g. domestic waste incinerators, paper making, and generally waste wood/plant matter decomposition, where hydrogen can cheaply be added to produce methane (pipes) or propane/butane (tanker trucks with liquified gas).

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