Update - June 2014

Not much has happened, the house is in need of repairs before I can decide to upgrade our energy system.
I just looked at heat pump forced air systems, and they are advertised to cut 30 to 40% of an electric bill, which seems low and pushed the ROI to beyond 10 years. So I am still considering a hydronic system that can use solar. It really seems a hydronic system is the best, with combined heat pump and solar heating.
Starting with the hot water system would also be a great way to learn how to build the heating system. A good first project would be the hot tub system.

Solat Water Heater Diagram

Our solar water heater will use standard parts. It will include two standard electric water heaters, one will be used as a solar tank. The heat will be transferred to the main water heater with a heat exchanger. The two electric heating elements will be removed from the solar tank, providing two access ports to connect the heat exchanger. The lower heating element on the main tank will also be removed, and a special tee will be connected to provide inlet and outlet to the heat exchanger. The upper heating element will stay for backup. The temperature settings will be 140F for the solar tank, and 130F for the main tank. A mixing valve will keep the hot water going out at 100F. The electric element will be set at 100F, which will be the min hot water temperature. Total cost (not counting the existing water heater) is about $1200. Payback is 2 years, assuming $50/month savings.

Assembly should start soon, and hopefully it will be installed on time to collect some of our summer heat.

Hot Tub Heat Exchanger

Brazetek has shell and tube heat exchangers, suitable for hot tubs. The smallest is 55KBTUh. I will have to measure the compartment inside the hot tub to make sure it fits. I will also have to decide if I want to keep the hot tub electric heater or not.

[ Hot tub heat exchanger ]

Physical dimensions for the hydronic coil

The furnace area where I intent to insert the hydronic coil has a maximum inside dimension of 25"x25". The air channel is 22"x22".
The brazetek catalog has several dimensions for coils. There is a pdf that lists all dimensions. A 20"x20" coil will have 20"x20" coil area, and 24.5"x24.5" outside dimension, not counting the inlet/outlet pipes. This is the size that will fit. The inlet and outlet pipes will come out of the duct through pipes.
I looked for a coil that I could insert at an angle, to increase the coil area, but there is none that would fit, and it would make installation more difficult, so I will order a 20"x20" coil and install it in the furnace. The coil won't be plumbed yet, since there isn't a solar system yet to connect it to. There will be a 20"x20" paper filter installed against the coil, upstream of it. I may also install filters at the two inlet grilles. This will improve air quality and prevent the hydronic coil from clogging with dust, which would decrease its efficiency. Due to the low temperature of solar heated water, I will need the coil to keep optimal performances.

Solar Panel Set

The solar panel was set this afternoon. I was too busy and forgot to take pictures. The panel is very heavy. For the next panels, I will change the design to make it lighter, using 1x cedar instead of 2x pine for the frame, 1/2 inch plywood for the backing, or remove the plywood and replace it with narrow cedar planks under the pex pipes, the end of the aluminum heat spreaders will not be backed, which should be OK.

I still have to connect the panel to the hot tub.

Blue Moon

The Blue Moon, Friday morning. Magical light.

Sunsets on Mars, and on Earth

Curiosity lander shot its first sunset on Mars.

Compare this to a sunset on Earth:

One would have to make sure the zooming was the same, that the aspect ration was respected ... but it still gives a good appreciation about how the Sun would look like on Mars, compared to Earth.
In reality, Mars being on average 1.5 times further from the Sun than Earth, the Sun should appear 1.5 times smaller there.

First Solar Panel Started.

I spent the whole afternoon today building the solar collector to heat our hot tub. This is an experiment to familiarize myself with the technology. About half of the panel is built, and hopefully, I will have it running by the end of the weekend. First was putting the heat spreader plates on top of the plywood sheet and mark each pex run.

Each line is where the pex tubing will lay. This will help, particularly with the problem I will encounter in the next step.

At the end of the first pex run, I had to bend the pex tubing to lay on the next line. Just to be sure I would not kink the tube, I checked on line the minimum bending radius: 5". My mistake was to think diameter instead of radius. I have 5.5" between lines, so that is 2.75" radius, too short. The solution was to go every 2 or 3 lines, and come back on the next run. Here the first two lines are laid.

Next, the four fist lines laid.

Seven lines laid so far, three more to go.

One more to go. All this done with a bending radius no less than 5".

Now the painting, after cleaning the plates with alcohol. One spray can of black rustoleum is not going very far.

I went tonight and bought a liquid can of high temp black paint. Writing the blog, I realized that there will be a problem with this design. With the way I laid the lines, it won't drain properly. That is OK for a hot tub that can be drained for the winter. For the hot water heater however, I will have to get pex that can be bent with a 2.75" radius, or find another way, such as running two lines in parallel. And that is why I started my solar projects with an experiment :-)

Backup Heat

One option for backup heat is using a heat pump water heater, a commercial type that can handle the load. The problem with that option is that the heat pump is unlikely to be running at the time I will need it the most, because the outside air will be too low. However, thanks to the 1-day storage capacity, I can set the heat pump to run only during the warmest part of the day, one extended cycle to bring the storage tank temperature up to 140°F, once a day.
Unfortunately, all the water heater heat pumps I found online are designed to work indoor, with intake air temperature around 20C, or 70F. I haven't found the right product yet. The heat pump is an air-to-water heat pump, with intake air temperature as low as 35F.
Another option is to use a geothermal heat pump. The heat pump must be designed to heat water, not air. Most geothermal heat pumps heat air, but there are a few that heat water, such as the water furnace. Looking at their website, it appears they have a design that is suitable for my application: Model 084.
Water Furnace
According to the performance table in page 5, the entering source temperature may be as low s 32F, with an entering load temperature of 104F, giving a COP of 3.1. This COP probably does not include the energy used by the two water pumps (load ans source). Instead of being connected to ground loops, the heat pump will be connected to an air to water heat exchanger. There will be a gradient between the water and air temperature, that must be determined (it depends on size of exchanger, and output of heat pump).
The heat pump can be set to run only of the warmest part of the day, such as late afternoon. A simple way to do that is a timer. A more efficient way would include a smart controller retrieving the max temperature for the day from a weather forecast, and start the heat pump when the temperature is less than 5F below the max. The 5F gradient should be determined by the amount of time the heat pump will have to run to bring 270 gallons from 100F to 140F.
The month of December 2012 was colder than average December months in past years. If we assume a 5F gradient for the heat exchanger, minimum temperature requirement is 37F. Every day in December 2012 exceeded 37F at their max. That doesn't mean they exceeded for long enough to heat 270 gallons. We need to make another assumption for that, such as the max temperature of the day should be 5F higher than the min required temperature to provide enough heat (number TBD for now). Minimum outdoor requirement becomes 42F. 11 days were not suitable. For those days, the electric strips will have to be used. Assuming a COP of 3.1 for 20 days, the overall COP for the month is 3.1*20/31 = 2.

Storage tanks

The initial idea of a 1400 gallon storage tank in the main downstairs room appears today unpractical. The alternative is too have a tank in the water heater closet, and another one in the furnace room, which means two separate systems.
The water heater closet can accomodate a 3' x 3' x 4' tank, with a chamfer where the tank will come underneath the stairs. Total water volume is 75 gallons. Total energy storage, assuming a usable temperature range of 140F to 80F, is 10KWh. That is about 1 day of storage in winter.
The furnace closet can accomodate a 4' x 4' x 5' tank, with a water capacity of 270 gallons, and an energy storage (assuming 140F - 110F temp range) of 20KWh, equivalent to 1 day of heat in the winter.
The location of the furnace tank would make it possible to reclaim heat from the upstairs wood stove, which would be a significant advantage, since the wood stove easily overheats the upstairs living room.
Because the systems will be separated, they will also need separate solar panels. The furnace tank will use the garage South wall, with up to 150sqft collector area. The water heater system will use the deck rail, 75sqft collector area. An alternate location is the upstairs South wall, with also about 75sqft area.
Optimum solar fractions (not accounting for cloudy days) is 84% for hot water, and 72% for space heat. Total solar fraction (also accounting other uses than heat) is 39%. Yearly savings is $600. Actual savings will probably be between $400 and $500. With a total estimated cost at $2000, payback is between 4 and 5 years.
Our total yearly electric consumption will go from 25MWh to 15MWH a year. Further efforts on improved insulation (windows and doors are leaky, walls could be improved, siding needs resealing and repainting) may reduce that to 10MWh. Net zero would then be achieved with a 6KW photovoltaic system.

Ground Source Heat Pump for backup heat

After building the solar thermal system, it would make sense to get rid of the forced air system all together. This will require a backup system that will heat the water tank in periods of low insolation. The most efficient system is a ground source heat pump for radiant systems, aka water-to-water heat pump. A 3-ton unit can be found on ebay for $3000. Problems have being reported after years of use of GSHP, due to the ground temperature changing over the years. To keep the efficiency of the GSHP high throughout the years, it is possible to use solar energy to recharge the ground loop. In my system, a secondary solar collector of about 120sqft would be used to heat the ground loop during the winter in periods of high insolation. The size of the solar collector is determined by the building that will hold it (a 14FT*14FT shed on the field that will hold the ground loop). To reduce cost, the ground loop will be buried at only 3FT, because we can rent locally 3FT Ditch-Witch units. Such a shallow loop cannot store heat seasonally, so the solar recharge must be used within days. The solar collector needs not be high temperature, so a pex collector, or even a pool solar heater, will suffice. I will use a pex collector build to fit the shed size. Because the GSHP is a backup, ground temperatures are unlikely to significantly change. It is not clear if the solar recharge will provide significant benefits. in the coming weeks, I will research on the backup system, solar assisted GSHP, and COP with solar recharge.

Wainscoting panels as space heaters

Now that our roof has been fixed, we can fix our damaged ceilings, and remove popcorn throughout the house. To enhance the look of our ceilings, we'd like to cover them with panels similar to wainscoting panels. Looking through the different options, I had a new idea for heat distribution. Wainscoting can be installed in walls of any kind of room, there are styles available for kitchens, living rooms, bathrooms or bedrooms, so we can conceivably install wainscoting panels throughout the house. We could use those panels as heaters, if we install a pex loop with heat spreaders behind the panels. That will give a significant surface, and will completely hide the heating loops. Some precautions would have to be taken during installation, but that should be a lot simpler than radiant floors, and more efficient too, since the wainscoting panels are rarely covered, unlike a floor. The cost of material for one room is below $100, so this is also a cost efficient option.
The heating system may have just 4 loops: 1 loop for each living room (because they have a wood stove), and one zone for all the other rooms, upstairs, and downstairs. The thermostat for the other rooms may be installed in each master bedroom (upstairs and downstairs).
So this idea put the focus back on radiant heating, since it becomes cost competitive with forced air.
The electric furnace would stay as the backup heat. No modification of the forced air system needed. I may upgrade the forced air furnace with a sequencer and a static pressure sensor controlling the blower speed, to allow for better zoning.
It seems the key to the efficiency of the solar system will be the size of the storage tank, which will likely be integrated inside the wall that will be built to separate the downstairs living room. The available tank size, removing the volume taken by insulation, is 2'x4'x12' = 1440 gallons. The tank will use a 12'x24' liner, and a heat exchanger made of 10' long copper pipes, for hot water, unless a separate solar hot water system is installed.

Thermoelectric dehumidifier

Thermoelectric devices are solid state heat pumps. Their main drawback is that they have a very poor efficiency, they use a lot of electricity that is wasted as heat. The key is to find applications that will use the waste heat. One application is a dehumidifier for cloth drying. Instead of dumping warm moist air outside in the winter, a thermoelectric humidifier can remove the water from the air and keep the warm air inside. A thermoelectric dehumidifier can also warm and dehumidify a bedroom, or a bathroom.
I started looking at how much it would cost to build such a dehumidifier. The cheapest thermoelectric element I could find is this one:
TEC1-12706.
92Watts max, about 60 Watts optimal under 12V.
The following heatsinks may be attached to each side:
DYNATRON G520.
The hot side can be equipped with a 80mm fan, such as this quiet fan:
Noctua NF-R8.
The cold side heatsink should be set downward, with a drip pan underneath to collect condensates. Some form of temperature control should maintain the cold side just at dew point for maximum efficiency. A hygrometer should turn on/off the dehumidifier when needed. I have a 12V 100Watts power supply that would be ideal for this.
Estimated cost: $70.
A more ambitious system would use 10 thermoelectric elements in series, powered by 120VAC through a rectifier. This would use 700 - 800 watts of electricity, and provide about 1KW of heat, considering the effect of dehumidification.

The small 100W dehumidifier could be set in areas of high moisture, while the 1KW dehumidifier could be integrated inside the furnace.

Producing heat, comfort and food

I have been reading from other people's experiences, particularly IWillTry.org, and got some good ideas I may try this coming winter.
First idea is to use dehumidifiers to increase comfort and produce some heat in the process. We could use two dehumidifiers in our home, one upstairs and one downstairs, each in the main living rooms. Our house is fairly damp, particularly downstairs, so a dehumidifier will increase comfort.
Second idea is to use a dehumidifier to dry cloth indoors. That should be fairly easy downstairs, by setting a small dehumidifier in the laundry room, with a drying rack. The dehumidifier could be set on a timer. For the upstairs laundry room, I will have to be a little more inventive.
Third idea is to grow plants indoors, using grow lights to compensate for short days. These grow lights will produce heat, that will heat the room. Basically, all the heat produced by the grow lights will be displaced from the main furnace. In theory, the grow lights won't use any extra energy. In practice, if I put the grow lights in the room where the furnace thermostat is, then the rest of the house will be a little cooler, or I will have to set the thermostat a little higher. Either way, it looks like growing plants indoor in the winter, using grow lights, does not use as much electricity as it appears at first. Plus I will have fresh salads all winter long.

Looks like I will have some fun projects this winter.

Good Solar Irradiance Reference

The following website is a good reference for calculating the amount of energy that will fall on a solar collector, depending on your location, the collector inclination, time of the year...

Solar Irradiance

I estimated my solar fraction using this calculator.
First of all, solar irradiance vs tilt:

I plan on installing two systems, one for hot water, and another one for space heat. The solar hot water system will be set against the garage, on a vertical wall, with some summer shading from the roof overhang. I used the following website to estimate how much shading the overhang will generate:
Sustainable Design.
Here is an estimation of the area of the collector that will get shaded, for each month:

Using these values, I can now estimate the solar fraction for a 100sqft collector (second row=consumption, 3rd row=solar fraction, 4rth row=savings):

I also calculated the excess heat provided by the collector, that could be used for space heating. The yearly value of this excess heat is estimated at $32.
Next, solar fraction for space heat, assuming a 300sqft collector (second row=consumption, 3rd row=solar fraction, 4rth row=savings):

The total yearly savings with a 100sqft hot water collector, and a 300sqft space heat collector, will be $776, out of a $1600 bill. Because we get bi-monthly electric bills, here is the savings for each billing period:

It is interesting to see that the Sep-Oct bill is lower than the Jul-Aug bill. Two factors explain that: the tilt, optimized for winter, and the overhang shadow. These are good features that will reduce summer overheating of the collectors.

Finally, i will add the estimated savings from a $8000 heat pump. The savings calculation assumed 73°F winter temperature settings (we are at 68°F), resulting in a $2000 heating bill (our total electric bill is less than $2000, with about 40% for heat, and 15% for hot water). Due to these false assumptions, the savings are inflated, so I applied a correction factor equal to the actual vs estimated heating bill:
Estimated savings from heat pump = $880 / year (assuming $2000 yearly heating bill).
Savings after correction = $352 (assuming 40% of $2000 total electric bill).

The solar system will cost less than $8000 (cost estimated between $4000 and $5000), yet provide twice the savings of the heat pump.
The solar fraction is estimated at 80% of heating bill, and 45% of total electric bill.

Hydronic coils

I have searched for hydronic coils to use solar heated water in our furnace. This coil appears to be the best for the cost:
Brazetek 24x24
At 230kBTU/h, it should provide some heat, even when the solar heated water is down to 110F. The static pressure on the blower may be a problem. I could also add a second coil, one upstream and one downstream of the blower, balancing the pressure while improving the heat exchange capacity.
Here is a page giving derating from lower water temperatures:
Water temperature derating
Assuming one coils as above (230,000BTU/h at 180F), the output at 140F will be 131,000BTU/h. At 110F, we can estimate the derating to be 0.28. The heat output will then be 64400BTU/h, or more that 5 tons of heating, which should be enough.
The coil will be installed below the blower, where there should be enough room. The assembly that will hold it, will also hold a paper filter upstream, to prevent accumulation of dust in the coil. The coil+filter will replace the old dirty filter that is there now.

I also found, from builditsolar.com, a source of solar tanks of big capacity:
American Solartechnics.
The best fitting tank for the furnace room is the 420 Gallons tank, measuring 43" x 76" x 54". That room could handle a 48" x 96" x 48", but that size doesn't exist standard. 420 gallons should provide enough storage capacity for most of the year. The tanks can handle 200F.
For the hot water system, their 110 gallon tank, at 34" x 34" x 54" will fit nicely. It could be coupled with a tankless electric water heater. The tank plus heat exchanger cost less than $2000. I'll have to compare that to other manufacturers. There is also the possibility of building it myself, which should be doable for the hot water tank, but difficult for the space heating tank, due to its bigger size.

Original Electric Furnace

In my quest to a more energy efficient home, I realized that re-using what already existed, and has worked for 20+ years, might be a good idea. Also, this is good for carbon reduction ("Reuse"). So that means I need to assess what I already have, as far as HVAC. Our home is equipped with an electric furnace from Lennox, model E11Q5-941-1P with Honeywell control. Here is a picture of the whole furnace:

Here is a close up on the label:

And here, the electrical wiring schematic:

From the information I have gleaned so far, this is a switched system, meaning it doesn't have a sequencer like modern electric furnaces. Instead, relays are used. Maybe this is a good upgrade to make, installing a sequencer. The blower is a 5 speed blower, although only two seem to be used (unlike what the wiring schematic says): Low speed for startup, then high speed.

Here are the features I can so far understand from the wiring diagram:
5 heat strips, or "element-electric heat", element 1&2 on circuit breaker 1 (CB1), element 3&4 on circuit breaker 2 (CB2), and element 5 + blower motor on circuit breaker 3 (CB3).
Each element has its own limit switch, although they are all called S2 on the wiring diagram.
Switch K1 drives the blower motor. This is the switch that is turned on when the thermostat manual switch is set to run the fan. If K1 is OFF, and K2 or K3 is on, then the blower runs at low speed. If K1 is ON, then the blower runs at high speed.

I will have to research a bit more to understand how the thermostat drives the different switches. It looks like upon a call for heat, the thermostat will close K2, which will run the blower on low speed, and energize HE1, 2 & 5. K2 AUX contact will close, possibly after a delay (?), and energize K3, which will turn HE3 and HE4 on.
I don't fully understand how K2-AUX work, or how K1 is energized (aside from the manual switch).

Before I think of adding solar heat to the system, I must understand how this furnace works, and how I can upgrade it to run an auxiliary source of heat.

Swimming Pool Heater

Yesterday, I was at a friend's house, and we talked about a swimming pool heater. His 24FT pool is cold, even in July. We talked about the idea of laying a 300FT coil of black irriguation pipe on the deck around the pool to heat it.
Doing some research, I realize this is not the best way to do it. One important requirement is that the pool heater must sustain freezing temperatures without damage. The simplest way to do that is to use a drainback system. A coil of pipe is not going to properly drain.
With that requirement, the simplest pool heater I found is based on the Thomason trickle collector, described [here].

The size of the solar collector should be at least half of the surface of the swimming pool, so for a 25FT circular pool, that is 75/2 ~ 40sqft.
The tilt angle should be optimized for the swimming season, so May through September. Ideal angle for September 1rst at noon is 40°, so the tilt should be at least that. We will use a 50° tilt angle.
The tilt angle, optimized for September, will reduce the effective size of the collector in June-August period, so the size of the collector should be increased to compensate for the increased tilt. Also, half of the surface of the swimming pool rule assumes June-August swimming season, September being cooler, it makes sense to increase collector size.

If we use standard Home Depot 6FT x 2FT corrugated panels, 5 panels will provide 60sqft of collector area, for a 6FT x 10FT dimension, which seems reasonable.
Since the pool is 24FT in size, depending on budget, we could consider a 6FT x 24FT collector, and increase the tilt, to further extend the swimming season.
A 6FT x 24FT collector would require 12 sheets of corrugated metal roofing. The frame supporting the roofing will be made of 2" x 2" x 8FT cedar studs. To make the building process easier, the collector can be build in sections of 6FT x 8FT. That way, we can decide to build one section now, and the rest later. One section will provide 6FT x 2FT x 4 = 48sqft.

Material:
6FT x 2FT corrugated roofing, 4 sheets at $12 per sheet = $48.
2 x 2 x 8 cedar studs, 7 studs for the frame, plus 4 studs to set the tilt, 11 x $3 = $36.
Black Rust-Oleum oil-based paint, 1 quart. $15
Rust-Oleum primer for Aluminum. $20
Galvanized outdoor screws.
Vinyl tubing.
Pipe brackets.
1/2" PVC pipe.
1/2" PVC end cap.
1/2" PVC Tee.
PVC cement.
[Pump]. $20

So far I am at $140 while missing some prices, so the total cost should come at less that $200.

Heat Pump bid

We received a first bid on a air source heat pump: $5500, installation included, 5 years labor guarantee, lifetime compressor guarantee. It is a Reem heat pump, but I am still waiting for a part numbers.
The air source heat pump limits how much we can use solar energy in our heating system, but I have being thinking on a some options.
The heat pump will not heat the water for hot water usage, so we will install a solar hot water system with electric backup. The storage tank will be made as big as can fit in the hot water closet. The South wall of the garage will be covered with solar collectors. We can install three 3'*6.5' panels, for about 60sqft total. If we buy ready made panels, that will cost $1130 plus shipping. If we buy the collector plates only, it will cost $600. It makes sense to build them ourselves, since they will be integrated in the wall of the garage. They will be protected from the weather by the roof overhang.
During the months when we do not use all the hot water, the excess hot water will be circulated through a heat exchanger installed in the air intake grids of the forced air system, giving some boost to the heat pump. I will have to design a system that will prevent drawing too much heat from the hot water tank for space heating, which would displace energy normally used by the heat pump, to the electric water heater, producing efficiency loss. Since the heat exchangers will only work at high temperature, it makes sense to use the excess heat from the solar hot water system to boost the heat pump. This system should provide a good efficiency during the Spring and Falls, but I don't expect the months of December and January to see much of an improvement from either the solar hot water and the heat pump.
I will detail the design in the coming weeks.

Solar Source Heat Pump

We have lost two of our tenants, which severely decreased our income. That postponed all remodel work. In the mean time, I have been thinking of different heating systems. One is to installed a closed loop water source heat pump that would extract the heat from the solar tank. The solar tank would be installed below the solar collector, with a capacity of about 2,000 gallons (30FT*3FT*3FT inside dimensions). The cold side of the heat pump (evaporator) is a heat exchanger that uses water from the solar tank. A mixing valve delivers a water temperature within the range of a standard heat pump, usually between 32 and 90F. The hot side is another heat exchanger, connected to the hydronic system.
The hydronic system could be smaller thanks to the higher water temp delivered by the heat pump. Baseboard heating would be adequate for such a system. The lower cost of the hydronic heaters offsets some of the cost of the heat pump. Some of the heaters, downstairs for example, could be home made using copper tubes.
The advantage of adding a heat pump is that more heat can be extracted from the solar tank. The colder water temp in the solar tank also increases the efficiency of the solar collector. The system will be able to run on solar for a longer period of time, but will also draw more electricity.
Alternatively, the most cost efficient system maybe a water source air handler type heat pump, that would re-use the air duct system in the house. This completely eliminate the cost of the hydronic system, and still give very good efficiency.
With a common rule of 600sqft/ton, we need a 4.5 to 5 ton system.
Another improvment of the heating system is to add zoning with these [ motorized thermostat controlled registers ]. The upstairs bedrooms and downstairs living room usually get overheated, so these rooms would get the thermostatic registers.
Ultimately, cost constraints will dictate the system, so my feeling is that we will probably go for a standard air-based heat pump with thermostatic dampers in strategic locations. Later, a solar heat collection system may assist the air source heat pump.