Homestead · energy
Energy
Every fuel that comes in, every machine it passes through, and every room, tank and line it ends in, for a year. Move the sliders and the year redraws: how much of the winter the wood carries, which boiler burns it, and whether the wood is cut here or bought.
woodpropaneelectricityheatkept by recoverylostwidths are energy; electricity drawn at 3,412 Btu a kWh
Scroll the diagram sideways
The fuels, a year
| Fuel | A year | What it costs |
|---|---|---|
| Wood, split, for the gasifier, the masonry heater and the sauna | 21 cords | $467 |
| Wood, the mills' 8-ft ends, for the outdoor boiler | 29 cords | $654 |
| Propane | 939 gal | $1,606–1,944 |
| Electricity from the grid, net of the panels | 35,567 kWh | $4,090–5,335 |
| Fuel and power a year | $6,817–8,400 |
Wood cut here is priced at the state's stumpage rate for mixed hardwood, $22.48 a cord, and nothing for the hours of cutting, splitting and loading; the sawmills' ends are counted the same way, as their own price is not yet known. Bought, seasoned hardwood at $275–450 a cord. Propane at $1.71–2.07 a gallon, the state's residential range last season. Electricity at a regional cooperative's $0.115–0.15 a kWh, the panels counted against the year's use; how the utility credits what they send back is not yet known.
What the year delivers
| Million Btu a year | |
|---|---|
| Heat delivered to every room, tank and tub | 650 |
| Cooling the house (the heat pumps, about 350 full-load hours) | 13 |
| Kept by recovery, not burned | 51 |
| Lost: up the flues, from the buried lines, through the tank's jacket | 583 |
Heat kept, not burned
- The ventilator. Fresh air for the house through an energy-recovery ventilator, 170 cfm at about 70% recovery: about 24 million Btu a year that would otherwise leave with the stale air.
- The drains. A copper drain-water heat exchanger on each of the house's two shower stacks, where they drop through the basement: the warm water going down the drain preheats the cold water coming in. About 2.3 million Btu a year, a small number that costs nothing to run and has no moving parts.
- The greenhouse's own store. The tank in the hub runs from 100 to 190 °F and can take almost none of a sunny winter day's surplus, which comes off the glass at 70–90 °F. So the greenhouse keeps its own: about 3,000 gallons in a buried, insulated concrete tank under the dining gallery, charged to about 80 °F by the fan coil under the ridge and drawn down into the beds' loop through the night. The climate battery under the beds takes its share first. About 25 million Btu a year comes back, most of it December to March.
- The farm's air. Each fruiting room's air passes through a heat-recovery core of its own, and comes in through buried pipes first.
The greenhouse, alive
The greenhouse grows the house's fruit: what goes in as sun, water, air and compost comes out as fruit, oxygen and water vapour. Eleven trees and a wall of espaliers on about 995 square feet of planted floor, a year at a time, young and grown.
| Fruit | Trees | Pounds a year |
|---|---|---|
| Apple, dwarf (M.9/M.26) | 2 | 80–160 |
| Sour cherry | 1 | 15–40 |
| Pear on quince | 2 | 60–120 |
| Peach, genetic dwarf | 2 | 30–80 |
| Fig, common | 2 | 20–60 |
| Meyer lemon | 2 | 16–50 |
| Espalier apple and pear, 22 ft of wall | ~9 cordons | 60–110 |
| Strawberry, Albion (hanging baskets) | 68 | 51–102 |
| Strawberry, Seascape (hanging baskets) | 68 | 51–102 |
Estimates for this house, from outdoor extension yields read low because the glazing passes about three quarters of the light; the tree mix is the one assumed for the estimate, two of each where a partner is needed for pollination. The balance is photosynthesis' own: the carbon dioxide taken from the air becomes the year's fruit, leaves and wood, and an equal number of oxygen molecules go back out. One bumblebee box at bloom, and a brush on the lemons. The compost is the mushroom farm's spent substrate, weathered half a year before it goes on the tree rows.
One conflict to settle: apples, pears and sour cherries need a winter rest in the cold, and the same sunny days that charge the warm store keep the house too warm for it. Figs, lemons and low-chill peaches don't mind.
What the mechanical and electrical cost
| System | Lines | Low–high, before tax |
|---|---|---|
| The hub's plant: wood, propane, the tank | 13 | $59,963–100,017 |
| Heat lines and floors | 8 | $39,595–72,787 |
| Fire in the house | 2 | $28,000–60,000 |
| Air: heat pumps, air handlers, the ventilator, humidity | 20 | $43,370–53,202 |
| Recovery: the drains and the greenhouse's store | 3 | $7,990–13,920 |
| The greenhouse and the bath house | 3 | $13,500–34,000 |
| Water and plumbing | 21 | $43,817–67,680 |
| Power: service, solar, battery, wiring | 10 | $79,289–155,818 |
| Light | 4 | $7,711–8,568 |
| Mechanical and electrical | $323,236–565,992 |
Materials and equipment from the drawings' own counts, priced from posted prices and makers' lists where they were found and estimated where not; the hired trades where they are hired, the owner's crew not at all. The container farm's fit-out is not in it. A concept's estimate: the real numbers come from quotes.
Every figure here comes from the drawings and their sources, and the estimates are marked as such where they are made: the heat loads by conductance and degree days, the electricity a first budget, the boilers at seasonal efficiencies rather than their ratings. The arithmetic is one function, run here in the page and in the private report, so the two agree.