Ramah Design

[Adam Roukema]

Hi All,

I've just posted the prelim design for the Ramah project. Here's how
it breaks down:

A radiator will be placed inside the Hogaan, most probably right in
the middle. We will have a solar thermal panel supplying the energy
for the system. The heat transfer fluid will run through insulated
copper piping. For cool not cold days, there will be a heat sink
under a concrete slab that we will pour outside the front door to be
used as an entryway. If the hogaan gets too warm, the fluid will be
diverted to the line through the concrete to regulate the
temperature. This slab will be heated, so in snowy winter days, it
may be possible to melt the snow right in front of the entry to help
them use the building more often. Take a look at the file that I've
uploaded to see what I mean.

Of course, there is a lot that we still need to do for this design to
be viable:

First, we'll need to get a hold of the radiator that has been promised
to us to see what it's efficiency is. I've contacted the person who's
donated it, so standby for updates on that.

Second, we'll need to determine the heat load of the Hogaan. This
will involve calculating the volume of the space to be heated,
determining our minimum temperature, ie. our delta T for the system,
and estimating the heat loss through all the surfaces in the Hogaan.
I have all the areas, thicknesses, and materials that we're dealing
with so it is just a matter of sitting down and cranking out the
calculations.

Next, we can determine the number of panels we'd need to support the
calulated load. At the same time we'll be able to determine the
length and diameter of the piping we need, and make calculations for
our heat sink.

Last, we'll be able to determine the requirements for our pump and the
PV panel that will be needed for said pump.

There are a number of assumptions that we are making with this design:

1. There is a minimum temperature that we can work with. Anything
lower will be too much for our system. The people using the system
will just have to know that on some days, it will just be too cold.

2. The system will have no thermal storage, so again, on very cloudy
days, those using the building will just have to know that it will be
cold.

3. The system will be able to handle all conditions within our delta
T on sunny days within a certain timeframe during the day. Clearly,
it will not be warm enough in the early morning hours. The three way
valve will serve as a temperature regulator, possibly in addition to
something on the radiator itself, and divert the hot fluid through the
heat sink.

In the next meeting, we will be discussing the design and doing these
calculations, so please review the design and come to the meeting
ready to get to work!

Let me know if you have questions.

Adam

[Sara Eatman]

That looks great.
To what extent is the building insulated at the moment? Is there
maybe an opportunity, if we can get the funds, to insulate the roof a
little better? That's usually the best bang for the buck. It may be
worthwhile to look at the cost trade-off between better insulation
(lighter load) with a smaller thermal system and the less insulated
structure with a bigger solar-thermal system. Then we also have to
work with the weavers co-op (is that the only group that needs to be
consulted?) for any changes.
right, then. keep up the good work

[Adam Roukema]

I just uploaded some sketches of the dimensions of the Hogaan. From
this, we can calculated the load required to heat the hogaan. I think
we're assuming a delta T of approximately 50 degrees with a min of 25
degrees F. So, assuming the coldest allowable temperature for the
outside can be 25 degrees, how much heat to we need to dump into the
Hogaan to keep the room at a comfortable temp, ie. 68-72 degrees? I
encourage you all to try these calculations yourselves, and we can
come together as a group to go over any discrepancies.

Let me know if you have any questions, as I'm sure there will be about
my deplorable 'engineering' sketch.

Adam