Category Archives: Heating

Feb 25 2 comments
Heating, Interior

How much money did I save using my woodstove this year?

We burn about a cord of firewood in our Jotul F-100 Wood stove every year.   Our primary source of heat is the oil fired boiler in the basement,  the wood stove is a supplemental or backup source.  On those really cold nights, of which we have had a few this winter, it is nice to sit around the warm fire.

I thought it would be interesting to see how much money we saved every year with the wood stove.  There are several factors involved in this, namely, the heat value of the wood we are burning, the efficiency of the wood stove, the heat value of the oil we are burning,  the efficiency of the boiler and the cost for the fuel.

fire wood

fire wood

According to Woodheating.org, (linked to by the DOE wood heating web site), black cherry contains 23,500,000 BTU/cord (assumes >20% moisture).  A cord measures 4 x 4 x 8 feet.  Of course, these numbers are approximations, but for my purposes, they will work.

My wood stove is 74% efficient, according the the manufacture’s data sheet.  Therefore, I get 23,500,000 BTU  x .74  = 17,390,000 BTU heat per cord of cherry firewood.

My Furnace is 84.5% efficient, according to the last time it was serviced.  A gallon of heating oil contains 139,000 BTU.  Therefore, I get 139,000 BTU x .845 = 117,455 BTU heat per gallon of oil.

If I burned a whole cord of wood this year, I generated 17,390,000  BTUs of heat for my house.  I therefore avoided using 17,390,000 BTU ÷ 117,455 BTU/Gallon oil = 148 Gallons oil.

I get my fire wood for free.  Heating oil costs about $2.76/gallon, so I saved 148 gallons x $2.76/per gallon = $408.63 which is a little too precise.  I’d say $408 ±5% to account for imprecise qualities of cord wood and wood moisture content.

We are almost out of fire wood for this year, on account of it being cold.  Next year when the solar heaters are attached to the side of the house, it will be interesting to see how much oil is saved.

Popularity: 3% [?]

Jan 13 18 comments
Environment, Heating

Clean burning woodstove

I took this picture of our wood stove chimney. Once the little Jotul F100 wood stove gets hot  this is the way it looks:

wood stove chimney with fire going

wood stove chimney with fire going

Clear.  According to the US EPA certification sheet, (large .pdf file) the Jotul F100 Nordic QT puts out less than 3 grams of particulate matter an hour.

non catalytic wood stove diagram

non catalytic wood stove diagram

Very little particulate matter is released from this stove because it has a baffle. When the fire box is above 400 degrees or so, all of the smoke is burned in a secondary combustion because the baffle mixes the wood smoke with fresh air at a combustible temperature.  This means that the stove is much more efficient, safer, and better for the environment.    If the smoke were not burned it would condense as creosote on the inside of the chimney.

Jotul F100 Nordic QT wood stove at operating temperature

Jotul F100 Nordic QT wood stove at operating temperature

Wood creosote is a brownish yellow sticky substance that is essentially condensed wood smoke.  Since wood smoke is combustible, wood creosote is also combustible.  In fact, it is a bad hombre, leading to chimney fires that can burn down a structure.  It is the reason why every wood burning appliance needs to have it’s chimney cleaned and inspected annually.

A properly installed, clean burning, UL listed, EPA certified woodstove is good for the environment as they produce no nitrates or sulfates while operating.  They are a great way to save some money on heating, especially if the wood source is free.

Popularity: 5% [?]

Oct 26 2 comments
Alternate Energy, Environment, Heating

Solar Hot Water Energy Savings

solar domestic hot water system

solar domestic hot water system

My Solar Hot Water System has been on line for one year now.  I thought I’d post some results on the energy savings thus far:

Before the solar hot water system was installed, we used on average 32 kWh/day.  This is a three year average and it was pretty consistant.  Now that we generate most of our hot water by solar instead of electricity, our average useage for the last 12 months has been 23 kWh/day.  You might say, big deal… 9 kWh per day.  We are now paying ¢18.3/kWh.  Therefore 9 kWh x 365 days is 3285 kWh or at our current electrical rate, $601.16.  This puts it right in the range I was expecting and agrees with all of the calculations I did beforehand.  I love it when that happens!

What is even better, over the summer, the electric rates were peaking because most of our electric is generated by oil and natural gas.  It was durring those months that we saw the most savings, our electric use dropped to 15 kWh/day vs. the previous 3 year summertime average of 28 kWh/day.

My payback time should be less than 4 years.

Popularity: 5% [?]

Oct 08 5 comments
Alternate Energy, Environment, Heating, Solar Energy

DIY solar panels, Part II

This is part II of how to make your own solar thermal collector to help offset heating costs this winter.  You will need a good south facing wall to mount this collector on.  In order to be most effective, the wall should be unshaded between 9 am to 3 pm daily.  Some defused sunlight shining through the branches of a deciduous tree is fine.

Preferably this collector will be mounted adjacent to a large reflective surface.  A snow field would be perfect, however, dry sand, concrete and water will also work.  The quality of the reflective surface is called Albedo, which in Latin refers to its “whiteness.”

Here are some albedo figures for some common reflective surfaces:

Material Albedo (percent reflection) Comments
Snow, new 80-90%
Snow, old 65-75% After one week
Sand, dry 35-45%
Sand, wet 25-35%
Ice 30-40%
Concrete (dry) 50%
Water (high angle radiation) 8% Sun angle relative to surface
Water (low angle radiation) 70-100% Sun angle relative to surface

Also, the lower the sun angle, the larger the reflective surface should be.  This is for two reasons; first, the law of reflection states:

  1. The incident ray, the reflected ray and the normal to the reflection surface at the point of the incidence lie in the same plane.
  2. The angle which the incident ray makes with the normal is equal to the angle which the reflected ray makes to the same normal.

Therefore, the lower the angle of the sun the further away the reflection point will be from the collector.

Secondly, the lower sun angle also means that the energy density of the sun light is much less.  A larger reflective area will aid in gathering more energy.

Solar Collector parts list:

Nomenclature Number Price each Price total
Aluminum cans 560 0 0
Solar Selective coating, Dampney Thurmalox* 2 19.95 39.90
Aluminum angle   1×1x96″  1/8 3 24.72 74.61
Aluminum metal lath 26 x 84″ 2 10.67 21.34
Aluminum angle 1×1x48″m .050 4 4.98 19.92
SunTuff polycarbonate panels 26×96″ 2 19.95 39.90
Polyisocyanurate insulation panel 4×8′x1″ 1 23.50 23.50
24 VDC fan, 224 CFM, Mouser 5912-7114N* 1 90.55 90.55
Draft seal, 4″** 2 5.86 11.72
Diffuser, air 4″** 2 14.95 29.90
Duct connector, 4″** 2 4.20 8.40
Diffuser, air 6″** 1 15.87 15.87
Duct connector, 6″** 1 4.25 4.25
12 watt PV panel, Sunwise SC12-12* 1 143.22 143.22
Snap disk fan control switch, Grainger 4E116* 1 18.66 18.66
1×8x96″ clear pine board 3 9.32 27.96
RTB sealant 1 tube 4.89 4.89
High quality urethane caulk 1 tube 3.34 3.34

*Not required for a passive system
**Quantities doubled for a passive system

Total, active system: $447.16
Total, passive system: $355.74

All parts except snap disk switch, PV panel, and DC fan were priced and purchased at the Home Depot.

Therefore, a passive collector needs to offset $355.74 in the first year’s use, an active collector needs to offset $447.16.  According to NYSERDA, the cost of home heating oil is currently $3.823 a gallon.  I need to save 117 gallons of fuel oil to offset the $447.16 collector cost.  Each gallon of home heating oil has 139,000 BTU. My boiler is 86 percent efficient, therefore, I get 119,540 BTU per gallon.

My solar collector needs to generate 13,986,000 BTU to save 117 gallons.

I expect the active solar collector I build to generate about 45,000 BTU per day.  The heating season lasts from October through April, or 212 days.  I expect 30 percent of those days to be too cloudy to generate significant heat from the collector.  I have 148 days of good solar resource, so 6,660,000 BTU can be expected.  That makes the payback approximately two years vs the one year original design goal.

Solar collector tools:

Ridgid MS1065LZ 10 inch miter saw

Makita 6213D 3/8 inch cordless drill

Ridgid R84001 3/8 inch cordless drill

Bosch 1587A Jig Saw

DeWalt D28110 rotary grinder

Construction details to follow in Part III

Popularity: 7% [?]

Oct 04 8 comments
Alternate Energy, Environment, Heating, Solar Energy

DIY solar panels, Part I

I have been working on this for most of the summer.  The problem with solar energy systems is that they are expensive.  There is no doubt that a photovoltaic (solar electric) panel will save energy and pay for itself in time, however, the initial outlay of money to purchase and install that panel is more than most homeowner’s can afford.  Solar thermal systems are likewise good investments, however, there associated systems are complex and need to be carefully designed and installed so that they function correctly.

What if someone could design a solar collector that can be easily built and installed by the average do it yourselfer.  This is the idea that I had and I think I may have something.

Here are a few design benchmarks:

  1. That solar system would need to be fabricated on site with standard power tools.
  2. It should be constructed of material readily available at most home improvement stores and the like.
  3. The system should be simple and easy to understand and troubleshoot.
  4. It should be simple enough to construct that anyone with basic carpentry and metal working skills can build it and install it.
  5. It should be efficient and relatively inexpensive, paying for itself in one year.

Those are the basic ideas I had and I believe I met most of them with my design.  What I was going for was something that would produce heat during the winter time and be optimized for cold snowy locations.

This solar collector is used to heat air, circulating air over a collector plate and returning it to the conditioned space.  Air heating panels are simpler to construct than water heating panels, their downside is that there is no storage capacity associated with them.  In other words, they work great when the sun is shining, but will not produce any heat at night.  They are suplimental heaters in most cases and cannot replace a central heating system.  That being the case, they can still save a significate amount of energy.

The main collector surface is made from aluminum drink cans.  The cans have the tops cut off and are stacked horizontally like this:

horizontal can solar collector

horizontal can solar collector

This arrangement is more work and requires more materials but it has several advantages over other designs:

  1. Each can becomes a mini solar receiver similar to solar receivers used on large concentrated solar systems.
  2. The array of receivers gathers energy more effectively because there is less reflected energy than an ordinary flat plate collector.  Once the energy strikes the collector surface, it is reflected down into the cans where the convex bottom aids in absorption.
  3. If mounted on a vertical south facing wall in front of a reflective surface such as a snow field or dry sand, the array will gather much more solar energy due to the increased insolation area.
  4. Aluminum is an excellent conductor of heat, thus the heat will move to the back of the collector plate, which will be cooled by forced air.

The main idea here is to make it simple yet effective.  Aside from the collector, a 250-300 CFM DC fan and a PV panel round out the system.  A small “snap disk” thermal fan switch turns the fan on and off depending on the collector temperature.

Part II will discuss tools and materials.  I expect the system to cost about $400-450 to build.  The most expensive item is the PV panel, which can be substituted with an AC wall transformer.

Part III will be a sysnopsis of my own system.

Popularity: 8% [?]