House Goals and List of Technologies Used

Goals

  • Affordable to construct and operate
  • Low embedded energy in construction and operation
  • Comfortable place to live with sufficient space and fresh air
  • All critical systems can function without utility power (Heat, Water, Cooking, Refrigeration)

Challenges

December and January are both coldest and cloudiest months of the year. The highest energy demand corresponds with the lowest solar energy supply. Any solar collecter designed for these months is over-sized for the summer months and vise versa. This is in conflict with the goals of affordability and embedded energy.

Methods (in order of importance)

  1. Minimize insulated envelope surface area per person while having sufficient interior space for all indoor activities.
    • Less surface = less material = less cost + less embodied co2
    • Less surface = less heat loss = less maximum energy requirement = less material needed to collect and store energy = less cost + less embodied co2
  2. Insulate
  3. Construct mainly of plant fibers and unfired earthen materials. Use metal and plastic sparingly. Minimal concrete
  4. Use solar energy when the sun shines.
  5. Collect solar energy for when it’s dark or cloudy and store it in the cheapest, longest lasting form available for the application. Warm Earth > Hot Water > Compressed Air > Chemical Batteries

Envelope

Tip: Living things, food, medicine, water pipes, and batteries need climate control. Most everything else: tools, clothes, appliances, etc can be kept in dry, uninsulated space. This can lower insulated surface area.

Super Insulation + Air-Tight + Basic Solar Orientation

Larson Truss Double Stud Wall construction filled with dense-packed cellulose insulation

Rubble Trench Foundation - Less concrete

Frost Protected Shallow Foundation

  • Less digging
  • Insulating the ground around the house is also needed for Cimate Battery or AGS (below)

Gravel Bag Stemwall - Eliminate concrete

Board and batton siding or a similar board on board beetle-killed ash

  • Low cost and embodied energy
  • Looks good and lasts without paint
  • Low weight and good drying abilities.
  • Can easily see signs of rot and replace a single board. The old board used to cook pizza.

Clay plaster inner wall surface

  • Low cost and embodied energy
  • Looks good without paint
  • Adds thermal mass to interior moderate temperatures

Solar Thermal

Sun Frost Energy Efficient Shower

Gray Water Heat Exchanger

Low Thermal Mass Sunspace (LTMS)- Homepower Issue 158 p70,72

  • Performs similar to a solar hot air collector.
  • Sun will pass though the sunspace and windows on the south side of the house for completly passive solar gain.
  • On cold, sunny days windows and doors on the south wall can also be opened for additional convective heat transfer from the sunspace.
  • Back-of-envelope calculation shows a 2kw electric space heater will keep the house warm with $400 / year of electricity. If the sunspace can provide 75% of the heating that’s a savings of $3,000 over 10 years.
  • Other benefits like clothes drying, sunbathing on cold, clear days, exercise space, heating during power outages, and experimenting with in-ground solar heat storage.

DIY Flat Plate Solar Water Heater

  • Drainback
  • Built into south-facing roof
  • PV Daylight-Drive water pump(below)
  • One collector / tank for the domestic hot water, One collector for the hottub

Climate Battery - 6 day heat storage

  • Hot air collected in the LTMS is blown through pipes a few inches under the house floor. The earth, rock, and concrete slowly releases the heat to the house over a few days.
  • The heated earth is kept dry and insulated from the outside.
  • Closed-loop operation: air is returned to the LTMS. Outdoor air is cooler than the return air.
  • Air blower is Daylight-Drive

Annualized Geo Solar (AGS) - 6 month heat storage

  • Hot air collected in the LTMS is blown through pipes buried 9ft deep underground where it releases its heat. The heat in the ground slowly spreads and rises though the ground to the uninsulated floor 6 months later. This way abundant solar heat of June and July can be used when most needed in December and January.
  • The ground around the house has a 20ft “cape” of insulation keeping the heated dry and insulated from above. $2,400 estimated cost.
  • Open-loop operation: air is released to the outdoors. Outdoor temperatures is higher than released air.
  • This uses the fan during the cooling season. The Climate Battery is used during the heating season. Both systems can use the same blower if we can adjust the speed.
  • Would having the greenhouse inside the climate battery help or hurt it? It would break the insluated “cape” but also be adding heat.
  • This would be an upgrade to the Climate Battery, but it might be well down the diminishing returns curve.

Solar Photovoltaic

90V “Daylight Drive” or “Direct Drive” PV - Run with the sun shines. When it’s dark stop.

  • ISEC = PV + resistance heating coil + Insulated cooking container
  • 90V Industrial DC Brushed motors “Baldor” and “Leeson” are good brands - Can handle 0-90v with no damage. Spin slower with lower voltage. Climate Battery and AGS blowers use these. Can power all kinds of shop tools.
  • 120V “Universal” AC/DC motors aka “commutated series-wound motor” - most small appliances such as blenders and vacuums without electronic controls will work on 90v DC. These motors may also not handle low voltages. Use during clear days. Don’t try on anything you can’t lose.
  • DC brushless motors with special DD controllers.
    • El Sid is a good circulation pump.
    • Sundanzer DDR165 Refrigerator uses a Danfoss brushless controller that is made for 10-45v DC from PV panels.

Compressed air tanks and well water pressure tanks

  • If I can think of a use for these I would prefer it to the options below. There is a conversion loss, but they’re cheap, long-lasting storage.

12v - 450w PV + 2kw-h LiFePO4 battery

  • Repurpose van system for lights, carging laptops, smartphones, and other small batteries.

240v-120v A/C Grid-Tied PV

  • Mostly for charging an EV. Are there EV chargers that directly connect to PV?

Things I’ve considered and might add later

Masonry Stove

  • Costs less than $1000
  • Easy to collect and store a few MMBtu of dry wood
  • Could collect charcol for other uses
  • Smoke seems to set off my allergies now, though a small start-up fan could push or pull smoke away from the wood loading door
  • Takes up a lot of floor space if indoors
  • Provides too much heat for a small, well insulated envelope
  • If I build one later it will be an outdoor wood boiler with a water loop to the house for hot water and space heating
  • I might also be able to design it to double as a summer pizza oven.

PV powered ground-source water-to-water heat pump

Sounds great if I find a unit that fits most of these…

  • DC powered (daylight drive is prefered, but I’ll settle for batteries)
  • Uses a refrigerant that won’t destroy ozone and has a low global warming potential such as R-600a or R-290
  • Comes in a 1 to 2 ton size
  • Space heating and cooling
  • Domestic hot water
  • Bury some of the ground loop at the peremeter of the AGS insulated “cape” to capture some of the heat as it leaves.
  • We can DIY install for $4,000

Thermochemical Heat Storage - Calcium Carbonate (Limestone, seashells, chalk, etc)

  • I haven’t heard of anyone doing all of this, but people have been burning lime in wood kilns for thousands of years.
  • It has an energy density between wood and gasoline
  • On long, sunny summer days “burn” lime, Calcium Carbonate, in a PV powered kiln at 1800 °F. This is well within the temperature range of a “Low-fire” home pottery kiln. Bonus points for capturing and storing the CO2 that’s released.
  • After the reaction is finished put a pot in the top of the kiln to use the sensible heat to cook a meal
  • Store the cool calcium oxide for months in a plastic bag inside a sealed plastic drum to stop it from absorbing moisture from the air
  • On a cold, cloudy day safely add water to the unslaked lime, calcium oxide, to cook, heat water, and/or heat your house
  • Use the slaked lime, calcium hydoxide, in mortar, tortillas, or for any of the other uses