.
The main principals:
- 1. The solar heat collected mainly in the summer is stored in the ground, cold in the winter.
- 2. The heat and cold storages are close to the house, almost always under the house.
- 3. Air is used as heat and cold carrier, since it does not freeze or pollute and is inexpensive.
- 4. The circulation of heat is so planned that electricity will not be needed even when delivering heat from the storage.
- 5. The solar collector panels form the roof that fits the architecture.
.
1. Solar energy has often been stored into water, but water has some disadvantages like the expensive structure of the tanks, the leakages and the fact that water does not support the construction. When soilworks as the heat storage no profound building of the storage is needed. In the simplest form the storage consists of c. 3 m deep ditches, dug with a trench cutter, and the heat insulation is attached to the sides. E.g. 10 cm thick flexible aluminium, iron or plastic air conditioning pipes for heat delivery are installed in the tracks dug in the center. It is better to make two sets of pipes; the other ones for bringing heat with air as the heat-transfer medium, and the other ones, filled with air (or water), for delivering heat into the living space and cooling pipes too.
Sometimes the heat storage has to be made more profoundly. The ground is removed from the heat storage - c. 10 cm thick layer of heat insulation is installed on the bottom as well as on the side walls. Water insulation may also be needed, depending on the circumstances. The storage is filled preferably with sand and the pipage is installed inside. Different sized rocks can be mixed with the sand to increase the density of the starage and thus the heat capasity, too. The sand is rolled so that it becomes dense and does not sink any more. Finally a heat insulation is installed on top of the storage. Stones should not be placed near the sides of the storage since, due to their higher thermal conductivity, that could increase the loss of heat. The distribution of heat in the storage should be such that the hottest spot is in the middle, which reduces the loss of heat. Heat for the domestic hot water is also taken from the middle, the heat of the earth being 50 - 70 degrees there. The best way to get hot water is to let hot air circulate through the boiler in pipes, or to install the hot water tank in the hot ground.
It is best to build the heat storage so that the hottest sunshine in the middle of the summer heats the center of the storage, and the sunshine during spring and autumn heat the edges. Furthermore, the delivery of heat from the storage can be arranged so that the air curculates from the edges to the middle. This helps reduce leaks of heat and the middle of the storage stays warmer. The delivery of heat from the storage is caused by gravity - warm air raises always upward - but demands rather thick ducts. Thus no electricity is needed. Warm air circulates between the storage and the house; a thermostat can be installed at the end of the duct to regulate the interior temperature. The regulation can also be manual. Because of the reproduction of the spore-producing mould the heating duct must be vacuumed every now and then with an extension pipe installed in the vacuum cleaner. The thermal value of sand and stone is about one fifth of that of water, counted according to weight, but about half counted according to volume.
2. The heat storage is best placed under the house unless there are special
reasons that prevent it
(e.g. rock - the thermal conductivity of rock is ten
times bigger than that of soil - in principle there
should be enough soil). In
some cases the heat storage can be on the yard, but it has to be close to
the
place where the heat is used. The heat storage has to be placed on the yard
when solar heating system
is installed into an old house, or when the residents
insist on having a cellar in their house. Even
then part of the heat (and cold) storage
should be placed under the house because of the pipage.
Diagram
Appendix I
The distances from the solar cells to the heat storage and particularly
from
the heat storage to the heated area (living space) must not be long, since that
will only increase
leaking, piping expences and flow resistance. For the heat
to rise with the force of gravitation the
heated area has to be above the heat
storage. The heat storage forms the foundation of the building.
That is why
the floor may sometimes feel a little too warm. But generally a warm floor is
only healthy
and nice, especially in cold climates, and the heat will be made
good use of. Some heat insulation may
be needed under the floor. A
sufficiently large heat storage is the area of the foundation x depth 3 m
when
the house only has one storey. A house with 100 square meters' living space
would have 300 m3
heat mass under it, numerically 650 tonnes, but
the exact amount is difficult to estimate; it could
even be twice as big. The size of the heat and cold storages depends among other things on the latitude of the house.
In practice there should be heat for at least
six months' need. The capasity
of the heat storage may grow many years, since
the heat loss becomes less while the surrounding ground
gets warmer.
3. Air is clearly the best heat-transfer medium when we consider a reliable, care-free heating system. A water system is, at least in winter, in danger of freesing which breaks the solar cells and the pipes. Water can leak from even the smallest holes and a complicated system almost always has minor leaks. During a hot season evaporation occurs so that water has to be added almost daily. Other fluids: salt water, glycol etc. are expensive and polluting when leaking. If they leak into the ground water they pollute large areas permanently. Their flow resistanse is high like that of water, so rather high pumping power is needed to transfer heat from one place to another. Only air is care-free and inexpensive to use. Small leaks do not harm since there is air all around us. Air flows easily with the force of gravity - no radiators are needed. The air does not necessarily have to be returned to the solar cells. The cells can take the air from the south side of the house under the eaves - where the air has already become a little warmer.
4. As has been mentioned previously, no external power is needed in withdrawing heat from the storage since the heat rises from the heat storage by itself, with the force of gravity, into the living space. For the heat to be sufficient and even the pipes have to be rather short but thick by their internal diameter. From the other end of the pipe air goes from the room to the heat storage and from the other end comes into the room from the storage. At the other end of the pipe there should be some kind of thermostat to regulete the air flow in the pipe. In the summer both ends are closed. It would be good if the air flow in the storage would be from the sides to the center as that would reduce the flow of heat to the sides and out of the storage.
Energy is needed to transfer heat from the solar cells on the roor down into the storage. A small electric compressor with power of less than 50 watts, e.g. a turbine with two vortex wheels, is needed to blow warm or hot air down to the underground heat storage with a power proportional to the sunshine. A termistor connection prevents the operation of the compressor in the winter. The compressor is best operated by at most a 0,5 m2 solar battery located up on the same roof. If that is too expensive the compressor can take its power from electrical network. That will also need some kind of electrical eye for power regulation. Hot air is collected from the ridge of the roof and carried down in a pipe about there where houses used to have a chimny. Somewhere in that pipe there is the compressor. A suitable diameter for the pipe is about 30 - 40 cm. A thin pipe causes not only resistanse but noises, too. On the other hand, a faint noise just tells that the system operates.
A hot water boiler has been previously mentioned, too. At its simplest it is a closed, 150 - 300 liters tank without insulation 'buried' in the heat storage. Water goes there in one pipe and comes out hot in another pipe. This water tank is placed in the hottest spot in the middle of the heat storage. The water runs on its own pressure, what ever that in different situations means.
5. It has been previously mentioned that a solar house binds the hands of the architect. This is true in two senses: a) The house has to have a ridge roof. b) The house has to be so situated that the solar side of the roof faces south. Other minor conditions are the ground quality (water free, rock free) and the fact that there should not be any big and tall obstacles nearby (forest, tall buildings).
The angle of the roof has to be at least so deep
that in the middle of the
summer, when most of the energy is collected, the Sun will shine
perpendicularly
to the roof. When the Sun shines perpendicularly to the roof
the heat under the plastic can rise as high
as to 100 degrees (oC.).
The air circulation could make sure that the temperature will not
rise above
70 degrees. In the 60th parallel the angle of the roof should be at least
90
o-53o=37o, which is the normal inclination
in modern houses. It is
important to gain a great intensity of energy on the
roof sometimes, since peak temperatures are needed
in the middle of the heat
storage. An even steeper roof can collect even more heat, especially if one
wants to collect more heat during the spring and the autumn. In that case the
heat storage can be smaller.
If the inclination of the roof would be 45
degrees the Sun would shine perpendicularly to the roof as early
as on the
first of May. This angle is best at all latitudes when we consider solar
energy. Supposedly
people do not want to live in houses that look like
experimental laboratories but rather like normal houses.
The most important
matter, the solar cell, has not been dealt with yet. The solar cell is here
very much
simplified, it forms part of the roof sturucture as it is the
surfacing of the roof. No heat insulators
are needed because the heat is
mainly collected in the summer. The outer transparent layer is made of
plastic
that has a wave-like cross-section profile; section c. 10-20 cm
(Figure profile).
The transparent
plastic sheet can be replaced by black corrugated iron sheet
that heats the upward flowing air under it.
The roof consists of two layers of
sheet, the upper one being corrugated iron and the lower one plain sheet
metal,
and air becomes hot between them, or of corrugated iron and a flat insulation
layer under it. These
do not heat air as well as plastic and sheet metal under
it, but in many cases, especially in the middle of
the summer, it is
sufficient.
When the sun shines on the roof the air between the plastic sheet
and the
underlaying or black sheet iron starts getting warmer. The solar cell on the
same roof produces
electricity for the compressor, that pushes the heated air
down to the underground heat storage. During
the summer the coupler is turned
so, that adjustedthe hot air is directed to the center of the heat
storage,
otherwise the air is directed more to the sides of the storage. The duct
branches underground
to reduce flow resistance.
When hot water is needed and the user
turns on the water tap, cold water flows
into the pressure tank heat storage in the middle of the , where it
is heated.
The already heated water flows from the other side of the pressure tank for the
user. Temperature
in the tank must be above 47 Celsius for Legionella pneumophila strains.
When it gets colder in the
autumn the covers are removed from the ends of the
pipes coming from the heat storage, and warm air starts
flowing into the rooms
regulated manually or by thermostates. Air circulates the faster the bigger
the
temperature between the living space and the storage is, the thicker and
shorter the pipes, the more there
are pipes and the wider open the ends of the
pipes are.
HEAT DELIVERY FROM THE HEAT STORAGE .
.
APPENDIX
A. A warm house
and warm domestic water are part of our basic security.
Of course that is not all, we need lighting and
energy for houshold appliances.
The amount of the extra energy needed can vary a lot - normally in the West
it
forms one third of the energy used at home, but it can be much smaller. For example the filament bulbs
must be switced, and Your following computer could be a portable, "laptop".
I already have.
B. It should be
mentioned that even the sauna can be heated with solar
energy. There are big covered holes on the floor of
the solar sauna situated
in the middle of the house. When the covers are removed the sauna warms up to
50-70
degrees. Water is thrown in the hole, where it evaporates slowly. The
water has to be thrown on larger
surfaces to make evaporation quick
(finnish sauna).
C. In order to optimize the heat collection
the system could include a
small processor to regulate the compressor and the valves with the help of
temperature sensors.
D. This solar heat system has been developed for a house with a one
and
a half floors. Heat can be led upstairs from the underground storage through a
pipe; no return pipe
is needed.
E. When the solar batteries become cheaper more of them could be
installed on the
roof, which would increase the amount of electricity recieved
for lighting and domestic appliances. The
energy production would be so
organised, that lowest on the roof would be the solar batteries with their
electricity production of c. 10% efficiency, and above that would be the
plastic sheet and the air space
with heat production of 50% efficiency. The
voltage of the solar batteries would be a little higher than
the general line
voltage (230 V), and join together with an elektric car, or a special transformer would
transform the electricity into
alternating voltage, and the extra would be fed into the general network.
The
transformer would contain thyristors, voltage transforming filters and
syncronizers. Since it creates
some heat it should be placed appropriately.
There would be two electrical meters: one for buying, the
other one for selling
electricity.- The meter is inspected by the same person who reads it: it must
not
cause electromagnetic disorders, for example. The system is much less
expensive than storing much power
in accumulators. Some of the electric power
can in this system be used for charging a small accumulator,
when needed
and when warm is not enough to store (holiday cottages).
F. Large halls, e.g.
sports -, railway -, exhibition - and industrial
halls, as well as churches can be heated similarly: a
sloping, south facing
plane is covered with solar cells - a compressor pushes the heated air under
ground
into the heat storage, from where warm air is conducted via air ducts
into the hall when heat is needed.
The compressor can get its power from
electrical network, too. The system will save money notably. The
roof can also
be arched, as long as the radius of curvature is big enough. Solar panels that
have a fixed
curvature or suppleness can also be used.made
G. The sunniest wall of a block of flats can
be covered with the
previously described solar panel. A compressor can draw the warm air down by
the wall
and push it into the underground heat storage, which could be in the
yard, too, for example under the parking
area, or even under the street.
Normally the sunniest wall has no windows, which makes the installing easy
and
economical.
H. The fact that heat comes from underground raises the question of
radon
radiation. However, the pipes carrying heat inside are tight, so that no
radon can get into the pipes.
It is important to pack all joints between the
pipe and the floor material.
I.
In the southern
latitudes heat can be annoying in the summer and a
warm floor can make it even worse. In that case it is
best to start collecting
heat in the autumn. Or why not store cold air in a piece of land during the
winter
to cool the air in the summer. This means, of course, that a more
complicated pipage and some other devices
are needed, which are not described
here. There would be a separate compressor for the heat and the cold
circuits.
The compressor of the cold circuit would also get its energy from the Sun
in the summer, and in
the winter it would get power perhaps from the network or gravitationally with warm difference, and would
be turned on to cool the ground when the temperature
sinks below 0o
centigrade. A small cellar can be built in the middle of the cold
ground, which
makes it possible to store food in a cool place even in
the heat of the summer. Entrance to the cellar can
be either from outside or
from inside the house. Considerable amounts of energy are used to produce
cooling
and coldness. J. Cheap solar cells to be rolled are needed to be installed on the roofs. The solar
cells will produce electricity for ( in future: lithium <~ Li+ ~> silicon nanowires) batteries of electric cars and mopeds keeping air clean and noiseless in towns or
produce energy for the general network. Nanolayer keeps solar cells clean.
Next Spaceliner
It is mostly separate from its base, but the screw fastening makes sure
it does not come off in a storm. About a meter wide transparent plastic sheet,
that endures heat well, or dark metal sheet, (iron or copper) reaches from the
eaves up to the ridge. Some lining compound should be added in the holes when
fastening the screws. The seams can be sealed with glue if desired. Plane
sheet is used on the ridge for air proof sealing. For reasons of appearance
the sheet can have matte finish top surface and a different shade, it could
even be tile-like, without harming the efficiency. The plastic should be
environmentally safe so, that it could either be re-cycled, melt or at least
burnt safely without harmful heavy metal emissions. Under the transparent
plastic there is a black sheet, it could be a painted or even rusted sheet
iron,
a red sheet will also do. This underlayer should be of iron for the
reason that it protects from fires -
fire must not spread from the roof easily
and especially not under the roof. The solar panel and possible
skylights are
placed under the plastic. The actual supporting structure, the matching and
the roof truss,
are under the iron sheet. Air flows from the eaves between the
plastic and the iron sheet, raises up and
is collected hot or warm from the
ridge of the roof and is led down. Minor air leaks, which occur e.g. on
the
ridge, do not matter. The plastic has to endure the UV-radiation of the Sun,
stay clear and endure heat
and cold sufficiently. These requirements for the
plastic are hard but achievable.
1
The unnecessary traffic can be reduced by favouring telecommuting at home. The telecommuting
can be improved by developing equipment and by changing attitudes. To every excavation and to every
electric cable is an optical cable to be append. Every mobile mast and many satellites serve as the link of the broadband.
Äänekoski
Finland
EU
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