Karen Walk

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since Apr 18, 2012
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VT, USA Zone 4/5
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Recent posts by Karen Walk

eggs are meat you don't have to kill

our chickens have a natural desire to go inside at night where it's safe (unlike our ducks!)
8 years ago
We turned a precast concrete manhole into a hot tub. It's heated by our Garn wood fired boiler. It stays full all the time and is well insulated so uses very little extra heat. In the dead of winter, we need to fire the boiler for an extra half hour or so in order to make up for the heat loss of having the cover off while we use it. With a well insulated tub, keeping it full and hot is the way to go. We do not use any chemicals to treat the water. We use sphagnum moss strips from Spa Naturally. Some day we might find a local replacement for the sphagnum. The moss strips go into a the strainer compartment on the circulator pump. The circulator runs all the time. Yes, it uses a little electricity all the time, but is much more efficient than refilling the tub each time with hot water.
8 years ago
one way to test how leak-proof your pond will be is to dig out a sample of soil, and build your ideal pond in miniature. Tamp it down, see how well it holds water. Also, make it overflow and see how the water flows.

I'm not really sure why you want to dump all the excess water onto your neighbor's property though - can you create a network of swales you can feed through the rest of your property? If you can rent or borrow a BCS walk-behind tractor with a rotary plow, you can make quick work of small swales:

8 years ago
In my experience, goats can use their horns to help insulate their heads from the shock of an electric fence if they want to push under it. After they got out, they also liked to lick the salt off our cars, running their horns along the sides of the cars in the process. If you happen to have a nasty goat, a nasty goat with horns is much more dangerous.

I don't have goats anymore, and most likely won't have them again - I loved the little creatures, but they were not eating poison ivy as was their job. If I get larger animals again, I may opt for more docile creatures, with no horns.
8 years ago
it's been a busy week for me, and I haven't heard much on this thread - is anyone out there waiting for the simulation results? It takes a little time to put this together - so if there's not a lot of interest, I'll go work in my garden instead! If you're interested, +1, or reply!

8 years ago
First, a correction - THERM was created by Lawrence Berkley National Laboratory (LBNL), not National Renewable Energy Laboratory (NREL).

Hi B - You hit the nail on the head. Sand will have different thermal properties depending on the type of rock it is, how tightly it is packed, how much water is nit it, etc. Any time you take a rock and break it apart, it takes up more space - about double from my experience. Even trying to pack it back together you'll have limited success. I think that as long as you have pieces that are large enough to be categorized as "sand", you'll have significant spaces between them. Adding materials that are smaller than sand - silt and clay - will help take up that space.

I think that using sand as an insulator is pretty intriguing. On a horizontal surface, you'd have to keep it dry. I can't think of how to use it vertically, but maybe dry sand layer just under a waterproofing layer in an underground greenhouse would work well. In real life, there are thermal mass effects - I'm going to run some simulations in EnergyPlus, sticking with our existing materials and using dry vs wet sand vs wood as a radiant floor material. For the sand alternatives, I'll assume a layer of earthen tiles on top. It'll take a day or two before I can get to this, so bear with me.

In real life there are MANY factors that affect performance. Not the least of which is user preference - thermal mass works best when the temperature inside the space is allowed to fluctuate. Here's how I'm going to set up the model - if there is something you are curious about, and want me to add as an alternative, let me know. I will be a bit choosy just to keep the total number or runs reasonable.

Model setup:

1. The model will be run in a 1,500 square foot passive solar house - clear glass on the south side, with some overhang for shading. Wall, roof and glass construction will be the same in each model run.
2. Thermostat - each model run will use two options for thermostat:
a. Heating Setpoint of 70 F; Cooling Setpoint of 78 F;
b. Heating Setpoint of 62 F; Cooling Setpoint of 86 F;
(feel free to suggest different numbers...)
3. Climate - I'll choose two climate locations - one cold & sunny, one cold & cloudy.
4. The model will include other typical loads inside the house, such as lights, appliances, cooking equipment and people. The loads will be typical of an energy-conscious family.

Bear with me, I'll give anyone who's gotten this far something pithy to chew on in regards to thermal mass.
8 years ago
Hi Joshua,

For your outdoor boiler - what are you using? Are you using a system that has a hot water tank for thermal storage? I have a Garn at my house - and it works great. 1800 gallons of water storage. Tarm boilers can also be provided with a thermal storage tank. If it's sunny in the winter, we can let our Tarm coast for a few days. When it's cloudy, we fire every day.

Also, for Mark's slab - are you suggesting installing temperature sensor in the slab so that he has the option to control the radiant based on slab temperature? I think that's what you meant...
8 years ago
Just read the PC mag article about these. Looks like valid technology, however, their intended use is to extend the life of throw away batteries. They do this by boosting the voltage and draining the batteries more fully. The life of rechargeable batteries can be significantly reduced by discharging them too far. The article mentioned that the product can boost the voltage of rechargeable AA batteries, but they don't provide information about how this affects battery life.

The voltage boosting technology has been around for a while, what makes this product novel is its size.

My take: cool product. Rechargeable batteries are still more environmentally friendly. Voltage boosting technology makes sense with renewable energy as long as the allowed discharge is coordinated with what the batteries can regularly handle.
8 years ago
Hi Jay,

I want to respond to your question. I don't know exactly where your numbers are coming from, but I think it'll help if I take you all the way through an example.

Let's do Oak Wood.

On this site: http://wiki.gekgasifier.com/w/page/6123766/Insulation%20Data

Oak is given a thermal conductivity of 0.17 W/mK

W (watts) is a rate of energy use.
m (meters) is a unit of length
K (Kelvin) is a unit of temperature

In my original post, I converted to units of thermal resistance, because that is how most people think. So we have:

1/(0.17 W/mK) = 5.88 mK/W

This still doesn't make much sense to people in the US because we are still stuck on IP units.

If you look at the website, there is a conversation table, and we can use it to help us convert to IP units. The IP units I choose are:

Btu in / (h ft2 oF)

Btu (British Thermal Unit) this is a measurement of energy, and is the amount of energy needed to raise one pound of water one degree Fahrenheit

in (inch) unit of length

h (hour) unit of time.

ft2 (square feet) unit of area

oF (degrees Fahrenheit) unit of Temperature

According to the conversation table, to convert from W/mK to Btu in / (h ft2 oF) multiply by 6.94

So, for IP units of thermal conductivity,
6.94*(0.17 W/mK) = 1.1798 (Btu in / (h ft2 oF))

For IP units of thermal resistance:

1/(1.1798 (Btu in / (h ft2 oF))) = 0.8476 (h ft2 oF) / (Btu in)

These units are very confusing but they are the actual units behind the R-value per inch I quoted above.
8 years ago