I was speaking with a colleague recently about what I’d like to do relating to housing, and I’ve repeated much of it here:
I’d love to build DHW system that is solar+on-demand. This would involve conventional solar thermal collectors running at between 60C and 70C, an insulated wax tank within the building envelope, and greywater heat recovery. One heat exchanger dumps heat into the wax when the sun is shining, storing heat in the phase change at something above 55C, and another draws heat out on demand at something above 35C. My math says about 3 T of wax is sufficient for an off-grid home filled with teenage girls to get through November.
I’d love to build a solar concentrator to pipe light into conventional buildings to provide hybrid solar. 10 Suns, or even 100 suns would be really interesting to me. The hybrid part would include small LEDs connected to solar panels and lithium batteries that would be entirely self-contained, so when the sun is shining in the room, the batteries are charging. Each light would be set to have a different background light level as a trigger to come on. As the light intensity dims, individual lights come on automatically, either as ambient light or task lighting. No penetrations in the building envelope, and a continuous gradation of lighting. Maybe they would share batteries in clusters…?
I’d love to find out how to do cooking off-grid. 10,000 suns can melt Bismuth (with a similar volumetric heat of fusion to water), at 271C. While that’s hot enough to use for cooking, I just can’t visualize how to store that safely, or what I would use as my heat exchange fluid, or how I would draw the heat out when I wanted to cook, or…
I’d love to build a system to store winter using ice as a phase change material. 17T stored in a straw bale vault replaces a refrigerator. 43T with a air-to-air heat pump provides all heating, cooling, refrigeration, and dehumidification (wanna keep you house at 14 C all summer?) for a well built house. The trick is to build a structure that is sufficiently flexible to avoid rupturing when the ice expands. I’ve got that…
I’d love to build a house in Ontario that doesn’t need a heating system. Build the walls and floors out of the soil you dig out of the basement, and have a thermal mass of hundreds of tonnes, and wrap in strawbale. It would be massive and passive (and I guess, glassive, since the south wall would be glazing). With the rest of those ideas, it would be entirely off grid, (except for cooking for now).
I’d love to use a DCFC to generate CHP using wood or farm waste as a feed stock. Hell, I’d love to be a vendor if such a product became available anytime soon. I heat with 6 Cord of wood per year, and spend about $2000/year on electricity. I’d love to burn 8 Cord of wood a year, and get all of my electricity for sweat alone.
My Sustainability design philosophy would be:
- use what you get for free (to be frugal)
- keep the energy in the form closest to the free source (to be efficient)
- understand the shadow that your system casts on the ecosystem (to be moral)
- resilience should not be abandoned for efficiency (to be adaptable)
I have had similar ideas especially about the degrading light. In all, you actually will not need to have that much lighting. The energy could be used to keep a fridge/freezer running. The reason why I say this is because we normally sleep at night so if we are up past sun down, the lights will only be on for a short amount of time.
Lighting energy could also be used to power sensor lights in the home. Bedrooms should be manual but hallways or public areas could be sensor. A cool installation I came upon once was a “fridge/laundry” light installed in the doorway of closets and pantries. When the door is open, the lights are on. When you shut the door, the lights turn off. All of these could be energy saving as well as energy using so as not to destroy the solar power supply.
Something to consider however is thermal heating. We use a lot of materials to insulate our homes and each region has a different way of doing it. However, if you go back in time, you could see how “home insulation” was done before just in the “skeleton” of the structure.
One such explanation and basic plans that use this method could be found in this book I found at our public library.
“Living homes : Thomas J. Elpel’s field guide to integrated design & construction” by Thomas J. Elpel.
PassivHaus (or Passive House, in the North American market) is an approach that massively limits the amount of supplemental heat required – we designed a structure that needed about $50 of heat per year, using modelling of the worst year on record. HUGE thermal mass, high solar gain. No AC required, because of that thermal mass. Good ventilation required, since the house is sealed up tight, with about 0.35 natural air exchanges per hour on a windy day – the rest must be via forced air. I would use the same concept, but with on-site soils filling geotextile tubes 2 feet wide and 4 inches high, stacked up as a curved wall to make a soil silo. Use geogrid, geotextile, and a membrane, filled with a foot of soil, to build the floor assembly, and suspend straw bale from the roof to make an insulated flat roof – perfect for a green roof, or a greywater filter system, or a combination of the two.