SUNFLOWER: OUR PASSIVE SOLAR HOUSE
The seeded flower turns; heliotropic
Sun-worshipping Fibonacci spiral.
We named our house “Sunflower,”
Powered by panels that turn with the sun
And by the turbine in the air,
Whirled by solar-heated wind.
The whole earth is a sunflower.
Our decision to build a new house on
part of our land near Bangor, Michigan, was prompted by an earlier
decision to retire from farming as I passed my threescore and ten
years. The decision to build a passive solar house which was to be
off the grid was informed by my work as an Environmental Studies
professor at Western Michigan University, and reinforced by our
values asa members and organizers of Green Politics groups since
1987. As Greens we believe in living in harmony with nature, and
this involved a commitment to renewable sources of energy where
possible. As members of an anti-nuclear group, “Palisades
we had protested against nuclear power and did not want a house
dependent on electricity generated with nuclear power orfossil fuels.
Beyond this, I have been a pacifist all my life and Barbara has been active in peace work in San Francisco and here in Michigan for many years. We understand the symbiotic connection between the development of nuclear power for electrical energy and for weapons. Moreover, our nation’s addiction to oil has led us to war in Iraq, which has the world’s second largest reserve of oil. Thus war is one of the “externalized” costs of oil, not included in the price we pay. Other such externalized costs include air pollution and the resulting acid rain caused by burning fossil fuels to generate electricity and, of course, global warming. The burning of fossil fuels adds carbon dioxide and other gases to the atmosphere and they trap the sun’s heat and create the greenhouse effect which warms the atmosphere. These costs of climate change are also not included in the price, but will be paid by our children and grandchildren. Given this knowledge of how things are inter-related, decisions about how we provide shelter are not innocent or inconsequential. And, given the reality of externalized costs, responsible decisions cannot be made simply on the basis of the initial price.
The ethical issues implied in
house also involve us in promoting passive solar design and the
techniques of renewable energy. We welcome visitors and show them
how the house works and are willing to be included in the annual tour
of solar houses in southwest Michigan. We believe that the
development of renewable energy is generally better for our society. It
can create more jobs in the building of a new energy
infrastructure. It can foster democracy as it makes local control of
energy sources possible, And, as renewable energy sources are
diverse and geographically spread out, they are less vulnerable to
disruption by hostile powers. Thus renewable energy is a safer way
to true homeland security. Dependence on oil, especially as it is
pursued by the Bush Administration, leads to fascism, to a
belligerent militaristic state under corporate control. Finally,
and most importantly, supplies of oil are limited and it is prudent
to use the remaining supply of cheap oil to create the infrastructure
needed for the inevitable transition to renewable energy.
In December of 2000 we contacted
Phillips of Cascade Building and Design in Portage. He had been a
student in my Appropriate Technology course at Western and went on to
a successful career as a builder of conventional houses. We trusted
his ability and were glad to see that he was enthusiastic about the
prospect of building a passive solar house. This was a first for him
and he did the research needed to build an energy-conserving house. We
worked with him to design a floor plan and the type of house we
wanted and by March of 2001 we had a building permit. We made an
estimate of our anticipated energy needs, which were about one fifth
of what we had been using in our old conventional house, and Richard
Oraweic of Back to the Future, Ltd., agreed to design and install our
renewable energy system. The battery room on the east end of the
house was constructed first and the photovoltaic panels were set up
just east of that in April. We then had solar power to build the
house and the project was under way.
We decided to build a saltbox style of house which is two stories high in the front, or south, side and one story on its north side. The basic dimensions are 32 by 40 feet, with the battery room and woodshed attached on the east end and a screened-in porch attached on the west end. The 16 by 40 foot “great room” along the south side includes kitchen, dining and living areas. The north side has space for bedroom, bathroom and closet, utility room and a cold pantry. A feature that opens up space in the house is a two-story open area in the center of the house. On the second floor it is separated with a railing from rooms on the west and east end which serve as a study, extra sitting room or extra bedrooms. There is also another bathroom upstairs for a total of nearly 1800 square feet. Cabinets and shelves were built by Conrad Kaufman.
I. Electricity from Sun and Wind.
The ten 100-watt Siemans
panels are mounted on a Zomeworks tracker that follows the sun from
east to west during the day and provides most of our electricity in
spring, summer and fall. A Solar Boost 50 MPPT (Maximum Power Point
Tracker) functions as the photovoltaic charge controller and shows
both voltage in the batteries and the rate of charging. Since
winters in Michigan are very cloudy but more windy, the Southwest
Windpower Whisper H-80 wind generator, also rated at 1000 watts and
mounted on 4-inch pipe 66 feet high, produces most of our electricity
in winter. This so-called hybrid system, using both sun and wind, is
an extremely necessary part of the total system. The electricity is
generated as direct current and the four 6-volt Surrette batteries
that store it, rated at 683 amp hours each, are connected for a 24
volt DC system.
The Sunfrost refrigerator, Sundanzer freezer, well pumps and all other pumps and fans that start and stop anytime automatically are all connected directly to the 24 volt DC system. A 2500 watt Trace inverter changes the DC current to 120 volt AC current for compact flourescent lights and other appliances “needed” for a middle class lifestyle, such as television, CD player, and a word processor. Needless to say, on cloudy and quiet days we exercise discretion about how many such appliances are used. Since the inverter itself uses about 15 watts to change DC to AC, it is wise that those appliances that go on and off automatically are on DC. At night the inverter is in its “search” mode but does not use any power. This efficiency of a DC system raises the possibility of an electrical system that uses only DC appliances. And since the cost of our inverter was about $2500 it might have been possible to bypass this cost with an all-DC system. Our system also requires both DC and an AC breaker boxes with switches for the circuits.
Another option, which we rejected because our house is about a quarter mile from the road, is to get connected to the commercial electrical grid and use it as storage of excess electricity from renewable sources and thus bypass the cost of the batteries, which was over $2000. This may be of value especially if the electric company is required to pay a fair price for the renewable energy put into the system. As far as I know this is not the case in Michigan, yet. But this option would be good for the conscience especially if more renewable energy is put into the grid than conventional electricity is taken out of it.
The total cost of our renewable energy system was nearly $25000 and the installer claimed that he gave us a good deal and that the cost should have been about $30000. Even if the subsidy of $3000 from the state, which encouraged renewable energy, is subtracted and if the (unknown) cost of building a power line in for a quarter mile were subtracted, it would still take many years at current prices for electricity to amortise the cost of the system. The system has worked without trouble or repair for over two years, but eventually we expect to pay for repairs. As rates for conventional electricity rise, renewable energy might be competitive in price, but at present this kind of system is justified on the basis of ethical rather than economic considerations.
II. Battery Room Ventilation.
Since batteries give off hydrogen
when being charged, it is important that the battery room be properly
ventilated. The batteries are in a plywood box on the floor and as
long as there is no danger of freezing the lid is removed from the
box and a window above the batteries is kept open in spring, summer
and fall. It is good to remember that batteries also operate more
efficiently when they do not get too cold. In cold weather,
therefore, the lid is placed on the battery box and air from within
it is exhausted by a small fan. At the same time a slightly larger
fan mounted in the ceiling of the battery room is switched on to draw
warm air from the main part of the house through an insulated duct.
This warms the temperature in the battery room, creates a positive
pressure in it, and helps to draw fresh air through the airtight
III. Heating System.
The heating system in
has three components: passive solar heating, the masonry stove, and
the hydronic heating in the floor. The house is designed for
passive solar input with many south-facing windows that have double
panes of low-emissivity glass. The heat that enters through the
windows is absorbed by the 5-inch thick concrete floor which is
colored a dark brown with pigment fixed with acid, and by the brick
masonry stove. Because the house is built very tight and extremely
well insulated, it holds heat well for long periods. Keeping warm in
winter is less of a problem than staying cool in summer. Curtains,
especially on the east windows where the early sun shines in, help to
curtail heat input. Trees shade the house from the low sun in the
west. And, of course, windows and doors have screens so they can be
opened. Summer temperatures in Michigan are usually moderate.
The “Heat Kit” masonry
by Doug Fry of Sturgis, is situated near the center of the house
facing the living room with the back of the stove in the bathroom and
the chimney in the bedroom. The heat from the stove is radiated 24
hours or more into these rooms and the rest of the house. It’s 17
inch by 17 inch by 17 inch firebox is designed to be fired once a day
or every other day. Air for the stove is drawn in through an
underground duct from the outside. When the stove is fired a damper
in the chimney is opened all the way so the fire burns hot and as
efficiently as possible. In two or three hours, after the wood, in
dry little logs from 2 to 4 inches in diameter, is burned and only
embers remain, the damper is closed to retain the heat in the stove.
The fire in the stove heats walls
ceramic brick on each side of the firebox which then radiate their
heat through the bricks for many hours. Because the heated air has
to travel up about five feet and then down to the floor before it can
go up the chimney it is necessary that the stove be warm before it is
fired. When it is cold it needs to be preheated with propane torches
placed in small openings on each side of the stove. Once it has been
fired the stove stays warm enough to start the fire again for at
least 48 hours or as long as 60 hours. Firewood is a renewable
resource and our stove uses only one and a half to two cords a year
which we harvest from trees already dead. As for carbon dioxide, it
will be given off either as a dead tree rots or as it is burned.
The cost of the
stove was nearly
$7500, and this includes the chimney. This may be slightly more than
the cost of a conventional forced air furnace with ducts and fans
might have been, but the masonry stove will probably last longer and
the radiated heat from the stove is much more gentle and comfortable
than forced air. We consider the masonry stove the best investment
in the house. Glass panels in the door of the stove allow us to
enjoy the fire.
The third component of the heating system is the hydronic heat in the floor which is radiated by circulating hot water in “pex” tubing buried about an inch or two deep in the concrete floor. The hot water is circulated by “El Sid” pumps activated by two thermostats in different rooms of the house. This system is especially useful in late fall or early spring on cloudy days with limited solar input from the windows and when it is not yet, or no longer, cold enough to use the masonry stove. Because the heat is not immediate (it takes about twelve hours for the floor to warm up) it is necessary to plan in advance based on weather forecasts. Sometimes, but rarely, it is so bitterly cold that hydronic heat is used as a supplement to the masonry stove. Two sources for heating the water in this systemwill be discussed in the next section, but the third source, the heat source of last resort, is the propane-fueled water heater in the utility room. With this hydronic system the house could be left unattended for an entire winter without danger of freezing.
IV. The Hot Water System.
Hot water is pre-heated by two
sources. One is a loop that thermosyphons through the masonry stove
and an 80 gallon storage tank on the second floor above and beside
the masonry stove. This loop preheats water whenever the masonry
stove is used. The second source of hot water is a set of two 20
inch by 144 inch solar panels that are mounted above the large south
windows on the first floor. These panels serve to keep sunshine out
of the house when the sun is high in summer, and, of course, they
preheat water whenever the sun shines. In order to prevent
freezing, the water circulating through the panels is a glycol
mixture, and it is circulated with an “El Sid” pump powered
small photovoltaic panel. The tubes from the panels give off their
heat to the potable water in the storage tank through a heat
exchanger as tubes circle around the outside of the 80 gallon tank. The
hot water is pumped with another “El Sid” pump from this
to the 40 gallon water heater on the first floor as demanded by the
temperature differential between the two tanks.
The cost of the hot water system was $2000 for the solar panels, $1000 for the 80 gallon tank, and a little more than $2000 for the pex tubing, pumps, plumbing, hot water heater and controls. Part of this cost can be charged to heating the house and part of it to providing hot water for domestic use. At times the propane water heater switches on but propane use is modest: about 160 to 170 gallons per year and this includes propane used in the cook stove in the kitchen. The initial investment in this hot water system will be recovered in a few years, far sooner than the investment in the electrical system.
V. Other Energy-Conserving Features.
In order to conserve heat in
stabilize temperature in the house at all times, the north side of
the house is earth-bermed up to four feet from the roof. Rainwater
from the long (29-foot) north roof is collected in a 300 gallon tank
set on the berm so it can be used for irrigation.
A cold pantry in the northwest corner of the house is insulated from the rest of the house and used to store canned goods and the freezer. A space under the floor of the woodshed, between the battery room and the main part of the house, has been made accessible with a trapdoor and serves as a root cellar. It is only four feet deep but works well to keep potatoes until spring. Since the energy used to produce the food purchased by the average American family is comparable to the energy used to heat the conventional home or to power the average family’s automobile, it is good to build a house where food can be produced and preserved. Raising fruits and vegetables for household use is a vital component of a renewable energy system. A clothesline for the solar drying of clothes is a similar kind of easily overlooked renewable energy application.