Energy-Efficient Housing a la PASSIVHAUS: Energy efficiency will go nowhere regarding buildings without a very strict, state-wide-enforced, building code. In Denmark, a recently passed law requires NEW residential buildings must be zero-energy. The US should follow THAT example.
Note my starting point is a house, NOT grid-connected, that uses at least 80% less energy for heating, cooling, and electricity than a standard house. THEN I add the below systems. In winter it will be challenging, as several days may pass with near-zero solar energy generation. At least a week's consumption of electrical and hot water storage will be required; of the storage system nameplate ratings, about 70% is available of battery capacity, as batteries are typically charged to a max of 90% and discharged to a min of 20% of capacity.
Here is an example of what CAN be done, AND it would be invisible, AND it would maximize fossil fuel and CO2 reduction, AND it would REDUCE energy bills of already-struggling households and businesses!!!
If one had a properly-oriented, free-standing house about as efficient as a Passivhaus, then energy requirements for heating, cooling, and electricity would be minimal, even in cold climates. For living off the grid, in a near-zero-CO2 mode, the house would need to be equipped with:
- A roof-mounted, PV solar system + a lead-zinc battery system + a hot water storage tank with DC electric heater + a system with DC pump and water-to-air heat exchanger.
- A roof-mounted, vacuum thermal solar system. Vacuum systems produce hot water even during the minimum winter irradiance periods, whereas standard tube systems do not.
- A gasoline-powered, 2 kW DC generator with 50-gallon storage tank to provide electricity in case of too little PV solar and thermal solar energy during winter, due to fog, ice, snow, etc.
- Any excess electricity would bypass the already-full batteries and go to the electric heater. Any excess thermal energy would be exhausted from the HW tank to the outdoors.
- A whole house duct system to supply and return warm and cool air, with an air-to-air heat exchanger to take in fresh, filtered air and exhaust stale air at a minimum of 0.5 ACH, per HVAC code.
- For space cooling, a small capacity, high-efficiency AC unit would be required on only the warmest days, as the house will warm up very slowly.
- For space heating, a DC electric heater, about 1.5 kW (about the same capacity as a hairdryer) for a 2000 sq ft house, in the air supply duct, would be required on only the coldest days.
NOTE: As space heating and cooling would be required for just a few days of the year, an air-source heat pump would be overkill and too expensive in this case.
NOTE: A future plug-in vehicle could be charged with DC energy from the house batteries by bypassing the vehicle AC to DC converter, provided the batteries have adequate remaining storage capacity, kWh, for other electricity usages.
NOTE: The PV solar and thermal solar systems need to be oversized to ensure adequate electrical and thermal energy during winter when the monthly minimum winter irradiance is about 1/4 - 1/6 of the monthly maximum summer irradiance. See below URL of monthly output from 2 monitored solar systems in Munich; 1/6 is about right in South Germany.