4. It's the comfort, stupid
● With apologies to Bill Clinton, but it's not about heating and cooling,
the humidity in the air plays a big role in how comfortable you feel.
● 80 Degrees can be quite comfortable at 20% relative humidity, and
miserable at 80%. It's a lot easier to get the water out of the air than
to cool it down to 65 Degrees, but it's much more important to make
sure the conditioned space is sealed up tight for this than for heating
a small leak can let in a lot of water vapor
● Part of installing the solar thermal system is a checkup to insure your
home is well sealed. Since there are no combustion products to be
concerned with, the seal can be much tighter.
5. This sounds too good to be true
● So whats the catch? Well, you can't plug your refrigerator
into it, if that counts.
● Electrical energy is, admittedly, the easiest form of energy
to transport over long distances, but if you rely on the grid
you might find yourself in a cold house someday, because
as we all know the grid goes down from time to time.
● So, I can't sell this solar energy-how can I recoup my costs-
what is the ROI? While you can't generate a cash flow, the
avoided costs should allow you to recoup the investment in
3-5 years, depending on if you can eliminate gas service to
the building.
10. Last slide
● From cave to comfort
● Heat vs humidity
● Sealing the box
● Year around comfort-water to water heat pump
● Controlling RH yields beneficial side effects,
mold and bacteria control, etc.
Editor's Notes
Now, for those of you who have not run from the room in fear, I want to assure you that this is as complex as it gets. I am including it for two reasons: If you don't understand these you cant design a system, so the fact that I do should give what I am about to say some credibility. Just like you don't need to understand how an automobile works to drive one, you don't need to be able to design a system to heat your home with one. However let me point out two things in each equation1) they each involve the temperature difference multiplied by some sort of area and 2)the quantity Q is the amount of heat transferred, which is different than the temperature.
A pot of water at 130F will feel hot but replace the water with oil and it would only feel warm. It takes more heat energy {Q} to get the water up to 130F than it does to raise the same amount of oil to 130F. We'll get back to that in a little bit. For now, lets look at the simplest home solar heating system on the planet. Putting solar panels on the roof is the first step no matter the panels you choose, all of them have an inlet for the cold water and an outlet for the heated water. Several things make it desirable to put antifreeze in the system, including increasing the heat stored in the fluid itself. The heated water is then sent thru connecting pipes to the floor pipes and gives up it's heat. Heating the house to 70 or 75 allows it to work as a heat batter;, though the optional heat battery is much more efficient at this.
And how cool would it be to have guests over and hear the comments about how warm and toasty your home is. The trouble with most solar thermal systems is they try and heat water. This is harder to do, Remember our first slide-one of the two basic things governing heat transfer is the temperature difference. More heat is transferred when the temperature difference is greater. This is intuitively obvious if you consider a cup of coffee goes from hot to warm quicker than it goes from warm to cold. A solar hot water system will also take much more space than a conventional water heater since you need to provide storage. Also, since much more fossil fuel energy is used over a 12 month period to keep the whole house warm versus a small amount of water warm, the payback will be much quicker. A solar heating system can take virtually no space since the components are on the roof, in the floor, or in the walls.
With the addition of a heat exchanger the system can preheat the water to your water heater, reducing the load on it, your energy bill and eliminating or reducing the time a family might need to wait between showers. No combustion means no cold outside air drawn in (less to heat) and forced air feels 4-7F cooler than radiant heat (fan effect). This means that when the house is heated to 65F it feels more like 70F when the gas goes away, the hole in the roof does as well.
PV is currently being touted as the way to go with solar energy. there are problems that will never be solved with PV. The flat plate problem is the greatest and cannot be solved. If you have ever seen your reflection in a pane of glass then you have observed that some of the light is reflected back towards you the image is ghostly and faint but if you get a friend and stand about six feet apart and look at the glass at a glancing angle, you notice their reflection is much stronger, Turns out much more of the light is reflected back if that is the case, And since the sun travels across the sky, This can actually prevent as much as half of the sunlight from ever reaching the PV solar cells and you cant generate any power unless they are in full sunlight. Evac tubes don't have that problem may 21 9-3 75% or greater 21 july
More efficient heat transfer with more pipe-larger area available
