Thursday, December 29, 2011

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.

Friday, October 14, 2011

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.

Saturday, September 24, 2011

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:
92Watts max, about 60 Watts optimal under 12V.
The following heatsinks may be attached to each side:
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.

Wednesday, September 21, 2011

Producing heat, comfort and food

I have been reading from other people's experiences, particularly, 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.

Wednesday, September 14, 2011

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.

Monday, September 12, 2011

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, 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.

Wednesday, September 7, 2011

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.

Monday, August 22, 2011

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.

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.

Thursday, August 11, 2011

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.

Sunday, July 31, 2011

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.

Monday, May 16, 2011

Property layout - first draft

The following picture presents the location of the solar collector compared to the house. It also shows its South orientation. The collector is 12Ft high, 32FT long. This location is far away from trees to avoid shading. The house may produce some shading at the end of winter days, but that should be minimal. The location of the collector is also higher that the level of the house, which will further reduce shading.
Also shown are the rainwater lines to feed our toilets and laundry rooms, as well as several outdoor spigots.

Routing the hot water lines from the collector to the tank won't be easy. The current plan is to locate the tank downstairs inside a wall separating the living room from the third bedroom, on the South side of the house. The lines must run downward continuously from the collectors to the tank. The only way is to go around the house, which will make the pipe run a little longer.

Monday, April 25, 2011

Whole System Diagram (version 1)

In looking for a location for the storage tank, I realized a tank sized to my solar absorbers will need to be 1000 gallons. I have planned on 500 - 600 gallons, inside the utility room, but 1000 gallons will not fit. The tank size was determined by the rule of thumb of 2.5 gallons per square foot of absorber. This allows a good efficiency of the absorbers, while limiting the risk of overheating. Although there won't be overheating with a drainback system, I do want a tank as big as possible, to have a storage of heat for our numerous cloudy days.
I decided to choose an alternate location for the storage tank: under the deck. There should be plenty of room for a 1000+ gallon tank, and the pipe runs won't be any longer, since the tank will be between the absorber array and the house. The only part of the design that needs change, is the hot water pre-heater. The longer pipe run between the solar tank and the electric hot water tank will decrease the efficiency of the system. So I opted for a heat exchanger, located next to the electric water heater. I haven't decided yet what kind of heat exchanger.

It will be complex and pricey, which is why it will be done in two phases. I may get 4 absorbers instead of just 2 for phase 1, since phase 2 has the 8 absorbers arranged in two banks of 4.
Next will be a bill of material.

Friday, April 22, 2011

Phase 1 Design

Phase 1 will provide hot water pre-heating, and two bedrooms with hydronic radiators. It will use two 8' * 12' solar panels using the Sunraysolar absorber plates. I compared the cost per sqft of each absorber plate model, and the 8*12 are the cheapest, so we will have to find a way to implement them.
Because they will be in front of the house, the solar absorbers will be set horizontally, with two header pipes, one above and one below, to connect the absorbers headers. Each header pipe will be 24FT long, 1.5" diameter.
I am not sure this configuration will work. I am concern with air being trapped in the horizontal risers as water raises in the vertical headers. One solution would be to not add horizontal headers, but without them the absorbers won't completely drain, so these headers are required. I am hoping the tilt of the absorbers will be enough to allow a complete fill. At this time a filling/draining test is the only way to tell.
Thermostatic valves are set on each hydronic radiator. This removes the need to add thermostats, zone valves and other expense and complexity. This is the way hydronic heating is used in France.

Here is the block diagram for phase 1:

Bill of Material:

  • Absober plates (8*12) = $428.43 * 2 = $856.86
  • Material for absorbers (Plywood)= TBD
  • Material for absorbers (4x4 posts) = TBD
  • Hydronic radiators SD70160G = $525.35 * 2 = $1050.7
  • Thermostatic valves = $58.90 * 2 = $117.80
  • Hydronic pump = TBD
  • Solar circulating pump = TBD
  • Pump Controller = TBD
  • Heat exchanger (300FT pipe) = TBD
  • Various piping = TBD
  • Tank material (2X4) = TBD
  • Tank material (plywood) = TBD
  • Tank material (insulation) = TBD
  • Tank material (miscellaneous) = TBD

Total = $2025.36 so far (still many items TBD)

Thursday, April 21, 2011

Heat Distribution

Heat distribution is important when using solar heated water. The heat distribution system must be able to use a low water temperature, the lower the better, so that most of the solar heat can be extracted for the tank, leaving the water close to ambient, and improving the efficiency of the collectors.
I have looked at radiant floors, baseboards, and hydronic radiators. I have summed up the pros and cons of each in the table below:

Radiant Floors:
  • PROs
    Wide heating area than can use low water temperature.
    The floors will be replaced, we can choose what we prefer.
  • CONS
    Very costly solution, labor intensive.
    The floor is an insulator, which offsets the advantage of a wider heating area.
    Some of the heat will be drawn into the concrete slab.
  • Estimated Cost > $10k

Hydronic basebords:
  • PROs
    Cheapest solution
    Heater directly in contact with the air (more efficient).
  • CONs
    Not enough heating area, which will increase the water temperature needed to heat the room.
  • Estimated Cost = $4k

Hydronic Radiators:
  • PROs
    Can be scaled up, to account for lower water temp.
    Heater directly in contact with the air.
    Can use a thermostatic valve, which greatly simplifies system design.
  • CONs
    Somewhat expensive.
  • Estimated Cost = $6k

Based on this table, the choice is hydronic radiators.
Heating needs for our house are between 25 and 50 BTUh/sqft. Aiming at the high end, we will need a total of 3000sqft * 50BTUh/sqft = 150,000 BTUh.

The BTUh value of hydronic radiators is calculated for a water temperature at 180°F. The solar system will be set at 140°F maximum. At a water temperature of 130°F, the derating is already 0.5, which sets the BTUh rating at between 50 and 100 BTUh/sqft.
The whole house will need between 150,000 and 300,000 BTUh.

Our bedrooms are between 120 and 160 sqft. A good choice to stay within the 50 - 100 BTUh/sqft range, and fit all bedrooms is the Myson SD70160G, at 13,000 BTUh, and $525.35.
The biggest rooms are the living rooms, upstairs and downstairs, at 33,000 sqft. Each will use 2 SD70160G, for 26,000 BTUh. Since each room has a wood stove, it is conceivable to put only one radiator in these rooms, and use the wood stoves for supplemental heat during the Winter. The system will be initially designed with two radiators in each of these rooms.
The bathrooms, stairwell and laundry rooms will use a smaller radiator, such as Myson SD6060G, at 4300BTUh and $200. There are three bathrooms, and two laundry rooms.

The total amount of BTUh is: ( 13,000 * 11 ) + ( 4300 * 6 ) = 170,000 BTUh

Because the hallways and other dead spaces are not heated, we fall on the low side of the required range. This is OK, since the solar array is not supposed to provide enough heat through the year. During December and January, supplemental heat from the wood stove will be needed. An additional heat source may also be added to the hydronic system (wood pellet boiler or heat pump).

Next step is to design the system for phase 1, which will heat our hot water and two bedrooms, using two solar panels. If everything goes well, the system will be scaled up to the whole house, and 8 solar panels.

Wednesday, March 23, 2011

Buget cuts and military expenses

Today I'll do some comparison between the proposed GOP 2011 budget cuts, and the military expenditures of the last 10 years. The GOP proposed budget cuts are based on yearly budget, so when they say $30M (millions) cut on the first item on the list, Flood Control and Coastal Emergencies, that is for 1 year.
To put things in perspective, I calculated how long it took our military in Afghanistan and Iraq to spend the same amount of money. $30M is 2 hours of war. In this case, the GOP is basically proposing to cut the Flood Control and Coastal Emergencies funds for one year, in order to pay back just 2 hours of war.
There are a total of 70 items. Here are the one that saddened me the most:
  • Economic Development Assistance = 57 minutes of war. Great choice in a time of recession.
  • National Drug Intelligence Center = 39 minutes of war. We don't have a drug problem in this country ...
  • Juvenile Justice = 9 minutes of war. Just 9 minutes of war!
  • NSF = 9 hours. Science has never served this country.
  • Food Safety and Inspection Services = 4 hours of war. Haw we never had food contaminations in this country.
  • WIC = 2 days of war. Wicked! If you can't raise a kid on your own, don't have one...
  • Family planning = 20 hours of war ... and you can't use birth control either! That goes well with the item above!
  • Substance Abuse and Mental Health Services = 6 hours of war. We REALLY don't have a drug problem in this country.

Anyway, here is the full list, enjoy!

1. Flood Control and Coastal Emergencies: 30 M$ = 2 Hours
2. Energy Efficiency and Renewable Energy: 899 M$ = 3 Days
3. Electricity Delivery and Energy Reliability: 49 M$ = 3 Hours
4. Nuclear Energy: 169 M$ = 10 Hours
5. Fossil Energy Research: 31 M$ = 2 Hours
6. Clean Coal Technology: 18 M$ = 2 Hours
7. Strategic Petroleum Reserve: 15 M$ = 53 Minutes
8. Energy Information Administration: 34 M$ = 3 Hours
9. Office of Science: 1100 M$ = 3 Days
10. Power Marketing Administrations: 52 M$ = 4 Hours
11. Department of Treasury: 268 M$ = 16 Hours
12. Internal Revenue Service: 593 M$ = 2 Days
13. Treasury Forfeiture Fund: 338 M$ = 20 Hours
14. GSA Federal Buildings Fund: 1700 M$ = 5 Days
15. ONDCP: 69 M$ = 5 Hours
16. International Trade Administration: 93 $M = 6 Hours
17. Economic Development Assistance: 16 M$ = 57 Minutes
18. Minority Business Development Agency: 2 M$ = 8 Minutes
19. National Institute of Standards and Technology: 186M$=11Hours
20. NOAA: 336 M$ = 20 Hours
21. National Drug Intelligence Center: 11 M$ = 39 Minutes
22. Law Enforcement Wireless Communications: 52 M$ = 4 Hours
23. US Marshals Service: 10 M$ = 36 Minutes
24. FBI: 74 M$ = 5 Hours
25. State and Local Law Enforcement Assistance: 256 M$ = 16 Hours
26. Juvenile Justice: 2.3 M$ = 9 Minutes
27. COPS: 600 M$ = 2 Days
28. NASA: 379 M$ = 23 Hours
29. NSF: 139 M$ = 9 Hours
30. Legal Services Corporation: 75 M$ = 5 Hours
31. EPA: 1600 M$ = 4 Days
32. Food Safety and Inspection Services: 53 M$ = 4 Hours
33. Farm Service Agency: 201 M$ = 12 Hours
34. Agriculture Research: 246 M$ = 15 Hours
35. Natural Resource Conservation Service: 46 M$ = 3 Hours
36. Rural Development Programs: 237 M$ = 14 Hours
37. WIC: 758 M$ = 2 Days
38. International Food Aid grants: 544 M$ = 2 Days
39. FDA: 220 M$ = 13 Hours
40. Land and Water Conservation Fund: 348 M$ = 21 Hours
41. National Archives and Record Service: 20 M$ = 2 Hours
42. DOE Loan Guarantee Authority: 1400 M$ = 4 Days
43. EPA ENERGY STAR: 7. 4 M$ = 26 Minutes
44. EPA GHG Reporting Registry: 9 M$ = 32 Minutes
45. USGS: 27 M$ = 2 Hours
46. EPA Cap and Trade Technical Assistance: 5 M$ = 18 Minutes
47. EPA State and Local Air Quality Management: 25 M$ = 2 Hours
48. Fish and Wildlife Service: 72 M$ = 5 Hours
49. Smithsonian: 7. 3 M$ = 26 Minutes
50. National Park Service: 51 M$ = 4 Hours
51. Clean Water State Revolving Fund: 700 M$ = 2 Days
52. Drinking Water State Revolving Fund: 250 M$ = 15 Hours
53. EPA Brownfields: 48 M$ = 3 Hours
54. Forest Service: 38 M$ = 3 Hours
55. National Endowment for the Arts: 6 M$ = 22 Minutes
56. National Endowment for the Humanities: 6 M$ = 22 Minutes
57. Job Training Programs: 2000 M$ = 5 Days
58. Community Health Centers: 1300 M$ = 4 Days
59. Maternal and Child Health Block Grants: 210 M$ = 13 Hours
60. Family Planning: 327 M$ = 20 Hours
61. Poison Control Centers: 27 M$ = 2 Hours
62. CDC: 755 M$ = 2 Days
63. NIH: 1000 M$ = 3 Days
64. Substance Abuse and Mental Health Services: 96 M$ = 6 Hours
65. LIHEAP Contingency fund: 400 M$ = 24 Hours
66. Community Services Block Grant: 405 M$ = 24 Hours
67. High Speed Rail: 1000 $M = l3 Days
68. FAA Next Gen: 234 M$ = 14 Hours
69. Amtrak: 224 M$ = 14 Hours
70. HUD Community Development Fund: 530 M$ = 2 Days

Tuesday, March 1, 2011

Estimated solar fraction

Using monthly insolation data, sun angle and collector tilt, it is possible to estimate how much of our home energy needs (based on utility bills) will be provided by the solar system.

The first important data is the solar energy falling on each horizontal square foot, daily average, for each month, in KWh/day/sqft (click on the table or graphic to bring full screen):

Check my earlier post for references on this data.
Sun angle, calculated for the 1rst day of each month, graphical representation, followed by monthly data:

Next we need to calculate the collector sun angle. The ideal collector sun angle is 90°. The graphic shows how the collector sun angle is calculated (example shows June data), and the following table, each monthly value, for a 70° tilt.

Formula is:
Collector Sunangle = 180° - Tilt - Sunangle

The data from the table shows that maximum efficiency (collector sun angle = 90°) is achieve during the winter months, which is the reason of the 70° tilt.

Next, the ratio between horizontal area and collector area is needed to estimate the energy per collector sqft. This ratio is C/A, as represented on the graphic.

Area Ratio = sin(Collector sunangle) / sin(Sunangle)

Here too, the high tilt angle favors the winter months.
From these data, we can calculate the KWh/day per collector sqft:

KWH/day/collector sqft = KWh/day/horizontal sqft * Area ratio.

It is interesting to see how much the variation in monthly insolation is reduced by choosing the right tilt angle (compare the table above to the first table).
Finally, the solar fraction per month, for a 400sqft collector at 48% efficiency (60% from commercial flat plates data, and 80% for the "DIY factor"):

The yearly solar fraction is estimated at 96%.
The same calculation with a 600sqft collector, yields a 100% solar fraction, while a 275sqft yields a 90% solar fraction.
The difference in solar fraction between 350sqft and 400sqft, is only 1%. The December solar fraction goes from 67% (400sqft) to 58% (350sqft).
It seems that the best size is anywhere between 350 and 400sqft.

Final data is the needed collector area per month. This data could be useful if I want to occult part of the collector to avoid overheating. I will try to use a drainback system, but even with drainback, the empty collector exposed to the sun will wear faster than a shaded collector.
Also the 100 or so sqft needed during summer are for hot water needs, so this data is helpful in dimensioning the hot water system alone.

Wednesday, February 23, 2011

Tilt and Sun Angle

In my previous post, I calculated the solar collector area according to electric usage in KWh/day, and solar insolation is KWh/sqft/day. One factor that I did not include is the collector tilt, and it is a very important factor.

The first thing is to decide for a tilt angle. If we want to maximize energy harvesting in the winter months, then the collector tilt must be the 90° complement of the sun angle at that time of the year, at noon. This online tool is very valuable to calculate sun angle:
[ Sun Angle ]

Here are the values calculated:
November 1st, noon, sun angle = 28°
Dec 1st = 21°
Jan 1st = 20°
Feb 1st = 26°

A tilt of 70° will maximize efficiency in December and January, because its surface will be exactly perpendicular to the sun direction. This is the tilt we will choose.

To calculate how much energy can be harvested, we must convert a 0° tilt area (the base of the KWh/day solar insolation data) to a 70° tilt. The conversion is:
1 / cos(70°) = 1 / 0.35

Now we can calculate the area of a 70° tilted collector that will provide the heat needed in December:
Electric consumption in December = 75KWh/day
Sun insolation in December at 70° tilt = 0.09/0.35 KWh/sqft/day = 0.257 KWh/sqft/day
Efficiency factor = 0.6 * 0.8 ~ 50%
Energy harvested = 0.128 KWh/sqft/day

Solar collector area = (75KWh/day) / (0.128KWh/sqft/day) ~ 600 sqft.

A 400sqft collector would provide 2/3 of our need in December.
Using sun angle and KWh usage for each month of the year, we can estimate how much of the yearly electrical bill will be provided from solar energy. That will be the object of another post.

Friday, February 18, 2011

Energy Usage in 2010

We have been living in our new house for 1 year now. The following graph shows our energy consumption. It is very high, our house is all electric, and not very well insulated.

Out total annual usage was 19,440 KWh, an average of 1620 KWh per month, 55KWh per day.
Considering the 6 cold months, average consumption is 72 KWh/day.

With these numbers, it is now possible to determine the area of solar collectors needed to provide 50% of our energy with solar.
First, the solar insolation is Seattle (in KWh/m2/day): [ Reference ]

The average daily insolation for the 6 cold months, October through March, is:
Winter insolation = 1.8 KWh/m2/day = 0.18 KWh/sqft/day
Solar panel efficiency is about 0.6 for flat plate collectors.
[ Reference ]
I apply another 80% factor to that, due to the imperfections of a home made collector. The total insolation comes out at:
0.18 * 0.6 * 0.8 = 0.086 KWh/sqft/day
The goal is to provide 50% of our needs, which is 72/2 = 36KWh/day.
This equates to 36 / 0.086 = 400 sqft.
This is the same number I got earlier (in the Carbon Masters presentation) using a different method.
Water Heating can be estimated between 1/4 and 1/3 of heating needs, or about 120sqft. This too matched the calculations made during the hot water system design.

Now that the numbers have been cross-checked with two different methods, I can finally proceed with the construction.

Monday, February 14, 2011

Energy Descent / Climate Change Personal Action Plan 2.0

I became aware of the Peak Oil predicament around 2005. After about two years of reading and learning on the issue, with an anxiety level rising, I decided to write an action plan. The amount of changes that must happen in our life was so overwhelming that some kind of plan was necessary.
I wrote my first plan in late 2006, in my earlier website (down now).
In May 2009, I re-wrote it, and added it to this blog. Here is the link:
Action Plan 1.1
We moved to a new house in early 2010. After one year in our new home, it is time to revise the plan again. This is version 2.0.

1. Finances. 6 month cash reserve more necessary that ever.
Generate income from your home, by renting empty rooms for example.
Pay off debts, starting with highest interests, or longest term debts.
Buy second hand, this also reduces both waste, and unnecessary manufacturing and packaging.

2. Food. Start a vegetable garden. Plant fruit trees. Built a greenhouse. It takes a lifetime to learn gardening, start now! Get laying hens. They can eat kitchen scraps, will provide fresh eggs, fertilize your garden, get rid of bugs and provide meat as stew hens at the end of their laying life (~2-3 years). If you have a lot of grass, get a dairy goat.

3. Fresh Water. Collect rainwater and use it for non-critical needs, like toilet flushing, cloth washing.

4. Reduce your waste stream.
Stop city garbage service, and haul your garbage to the dump. Buy 7 garbage cans, that will match their flat fee.
Star a compost system to remove organic material from your waste stream.

5. Energy. Build a $1000 solar water heating system, as described here. If you have the skills, extend the system with radiant heating.
Use a local source of heat. Here in the PNW, that would be a wood stove.

6. Food Storage. Store food that is not easy to grow, such as grains, sugar ...
Build a solar dehydrator, learn how to can.

7. Grey Water. Nothing in Nature is a waste. Grey water from the laundry can be used to irrigate shade trees. Water loving trees such as willows will thrive, and their leaves are good forage for goats.

8. Transportation.
Get a sub-compact stick shift car. They are cheap on the used market, reliable, fuel efficient, and are enough for most people. A 2-liter 4 cylinder manual car can easily haul a 4X8 trailer.
Get a bicycle and train yourself now.

9. Sewage. We may eventually find that using drinkable water to flush the toilet is an obscene waste. Even rainwater may become too valuable for this. Learn how to use a saw-dust toilet, they are cheap and allow to safely dispose of our sewage. If water distribution is interrupted, it won't take long until Cholera sets in, as seen in disaster stricken areas.

10. Skills. Modern convenience has led use to loose valuable skills. Learn skills that allow to provide for your needs without using energy.

Tuesday, February 8, 2011

Solar Hot Water System Design

The solar hot water system will be the first improvement I will attempt to our current residence. This post presents the sizing of the system.

First parameter to consider in the number of occupants of the dwelling. We are currently 7 persons living in the house. We will soon be 4 only. Average occupancy in the future will likely be between 4 and 7 people. This is a 5 bedroom house so the system will be sized for 6 adults.

Solar Collectors.
Rule of thumb is:

  • 20sqft for each of the first two occupants
  • 12-14sqft for each additional occupant
  • 80% efficiency of the home made panels

[ Reference ]

This gives an area of 110 to 120 sqft for 6 people, and 95 to 102 sqft for 5 people.

We will use solar absorber plates from [ Sunraysolar ], which provides several dimensions:

  • 4FT * 8FT = $275. 3 panels provide 96sqft ($825), 4 panels 128sqft ($1100)
  • 4FT * 10FT = $322. 2 panels provide 80sqft ($644), 3 panels 120sqft ($966)

Three 4*8 is just enough for 5 people at a cost of $825, while three 4*10 is enough for 6 people, at $966. Although the 10FT panels are a better choice for area, the 8FT will be easier to build using 4' * 8' OSB boards.
Sunraysolar sells separately the fin tubes. Building the absorber using fin tubes costs about half, but requires soldering the fin tubes to the copper header. This also allows to build the absorber to the exact dimensions allowed to fit the site, so I may go this route.
At this time, I will assume the collector will use three 4X8 FT absorber plates.
The solar absorber plates will give a higher efficiency to the panels. The 80% figure assumes pex tubing in the collector, while I will be using copper pipes with aluminum spreaders. Although the collector is slightly under-sized, the higher efficiency should compensate.

Storage Tank.
There are different rules for tank sizing. I used the following website:
[ Reference ].
A rule of thumb is 10 to 15 gallons per person per day, or about 75 gallons for 6 persons.
Another rule of thumb is 2.5 gallons per sqft of collector area, which is 300 gallons for our 120sqft collector. This represents 4 days of storage for 6 persons, a good feature to have in our cloudy climate.
A 300 gallon tank will approximately be 3.5 ft cube.
Silicon solar (reference for the collector area) gives a rule of thumb that results in a smaller tank size. I don't think there is a drawback in having a bigger tank, except that it will take longer to heat the water after a series of cloudy days.
The tank will be build with 4FT sections of 2"*4". With the added insulation, the capacity should be slightly less than 300 gallons.

It will be a drainback system, so there is a head to account for in sizing the pump.
Solar absorber flow rate = 1.3GPM per absorber = 3.9 GPM total ~ 240 GPH ~ 900 LPH
The head depends on the location of the absorber. I have three locations in mind at the moment, on the roof (head ~ 25FT), against the garage wall (head ~ 18FT) or against the electric fence (head ~ 12FT). Eventually, there will be a collector in each of these three locations. The pump for each location will differ, due to the different heads. That means that there will eventually be three pumps. To reduce the number of inlets and outlets, all three pumps will be inline pumps, located outside of the tank.
I will assume at this time that I will chose the lowest head, 12FT. Now I need to find a pump that has 240GPM flow rate and a maximum lift of at least 12FT.

The major components are now defined:

  • A 8FT * 12FT solar collector.
  • A 300 gallons storage tank.
  • A 240 GPH Pump, 12FT lift min.

With those values in hand, I can now make a better decision as to where to locate each element of the system.

Monday, January 24, 2011

Our Energy Allowance

In order to shift our society from fossil fuel to renewable energy, we need to know how much renewable energy is available, how much daily solar allowance can we count on? One study shows that there is more energy reaching the Earth from the Sun in one hour, than the entire world uses in one year. It seems there is plenty.

The following model tries to determine how much solar energy can be harvested on a global scale, it doesn't look at what we actually use today for transportation, food, or other things. This is how much we get, whatever we do with it.
The model uses the area presented by the Earth to the Sun at any time, 24/7. For that, I used the area of the disk presented by the Earth, instead of the surface area of the Earth itself, which, because it is a sphere, would receive variable amounts of energy depending on latitude and time of day. Using the surface area of the Earth would require going through multiple use cases, while using the disk that the Earth presents to the sun at any time, allows to determine the global energy received from the sun, regardless of latitude, day-night, equivalent sun-hours or other fancy formulas. This is what we get on a global scale.
The model doesn't tell how we will harvest that energy. Again, this is another problem. Before we decide how we will harvest it, we need to know how much we get.

So here we go...

Solar irradiance = 1400 W/m2 at the top of the atmosphere. This is the amount of solar power on a one square meter area. The atmosphere will absorb and reflect a part, so it is estimated that the average amount of solar power reaching the Earth surface is ~ 1000 Watt / m2.

[ Solar Irradiance Reference ]

Now we can calculate how much square meters the Earth presents to the sun.
Diameter of Earth = 12,000 km = 12*10^6 meters
Radius = 6*10^6 meters.
Surface presented to the Sun = PI * (6*10^6)^2 = 113*10^12 m2.

The total amount of energy reaching the Earth surface is:

113*10^12 m2 * 1000 Watts/m2 = 113*10^15 Watts.

About 70% of the Earth surface is covered by water, so 30% remains. Of those 30% land area, we can assume that covering 1% of the land area with solar panels would be a maximum practical ratio, so 0.3% of the total energy may be harvested.

113*10^15 * .3% = 34*10^13 Watts
This is the amount of electrical power we receive from the Sun over 1% of the land area.

We are 6 billion people, so we need to share this power.

34*10^13 / 6*10(9) = 56 KWatts per person

Energy is power multiplied by time.

56*10^3 Watts * 24 hours ~ 1.3 MWh / day / person.

This is the solar allowance each of us can use before we start depleting resources.
Now this is before conversion into useful energy. The average conversion efficiency is about 20% for electricity (best case).

[ Photovoltaic Efficiency ]

Converting all of our solar energy allowance to electricity, we would have:
1.3 MWh * 0.2 = 271 KWh / day / person

Now lets see where we are today in the United States, as far as energy usage per capita.

Total energy usage of USA in 2005 = 29*10(15) Wh
US population = 300 Millions = 300*10(6)
Energy usage per capita in 2005 in the US = 100 MWh/year = 280 KWh / day / person.

[ US Energy Usage Reference ]

We can fulfill our electrical needs if we cover 1% of the land surface of the Earth with solar panels.