Annie Hope

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since Mar 05, 2012
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Recent posts by Annie Hope


As well as making a classic thermal mass rocket stove with 44 gallon drum on top as re-burner, I am also wanting something that will just heat a large pot really fast and then keep it at temperature for a while - for canning jars, pasturising straw for mushrooms etc.  This will often be in summer when we don't really need the thermal mass.

What will do this faster and more wood efficiently, a basic fire-bricks rocket stove with the flame directly on the pot, or sitting the pot on top of the 44 gallon drum re-burner?
3 weeks ago

The main purpose of the lean-to is not to be a greenhouse for plants, it is mean to:
- Act as a cheap retro-fitting double glazing on the house, with thermal mass heating it as well
- To extend the area of the house that does have dry soil underneath (we have a pier and beam house that does not have plastic on the ground under it, so we are going to do this under the house, and also in the greenhouse area, and put stones top of the plastic to make a thermal mass.
- To act as a retro fitted fly screen in summer and shading of the west windows from afternoon sun.  We plan to high-power fan vent the greenhouse out, and can open the house windows then as well.  Otherwise we have a choice of flies or a hot house in summer.
- To expand the living areas of the house - e.g. put a large dinning table in the greenhouse area near the kitchen, and a court-yard retreat from the guest bedroom.

There will be plants in pots and the outer corners of the greenhouse, but we will also have heat-exchange ventilation installed as well, so that should also control humidity.
3 weeks ago

I am trying to store heat in a lean-to green house round the house to try and store heat to release at night and help stop heat loss from within the house itself (esp. the single-glassed windows). 

I am lugging home several bags of river stone and sand on the way home from church every week to make a gabion wall and rock stove and portable thermal mass, but I have also noticed that wood has quite a good heat-holding capacity when compared to sand and rock.

A google brought up this article:

On the other hand, it is also insulative, so how quickly it will give and release heat I am not sure.  But in theory, a good way to go would be to make a wood box that was a gabion wall on the outside (for aesthetics) - like this:

If we then put the wood inside, and then a wooden top to form a seat - if we pull in the heat from the top of the greenhouse to the bottom of the box with venting tube as a fan, it should help heat the wood, and also super dry it - a wood drier is another thing on our to-do list!

Anyone tried this yet?  Any other ideas or suggestions why this would not work?

Otherwise I will keep you updated 0 and if anyone lets me know how to attach pictures, I will do so.

4 weeks ago

I know that a panel heater works best when built into a greenhouse type frame, and insulated at the back, but what about the evacuated tubes?

I am retro-heating our house with a mixture of passive heating (making a greenhouse lean-to on our sun-facing wall with thermal masses added) and radiators that are heated with evacuated tubes solar panels to store heat for rainy days.

My question is whether it is better for the evacuated tubes to be within the warmer greenhouse, or if they will work better sitting outside getting direct radiation from the sun.  We have average winter temperatures here of 2C to 13C and never on record under -4C as we are 7km from the beach, so freezing is not an issue.  (And my design will be drain-back anyway).
4 weeks ago

I got second-hand a number of hydronic radiators, and now want to get the risers and water storage tank to get these working.

As anything like that is so expensive here in New Zealand, I am looking at getting a one-off shipment from China, but want to do the maths on what I need for size.

I have a sort of insulated, very drafty 100 square metre / 1000 square feet house.

In winter our average minimum is 2C and and record minimum is -4C as we are near the coast.  I am aiming at 16C.

We are going to make an enclosed porch running the sun-facing length of the house that we hope will pretty much solar heat it on sunny days, and help stop the drafts.

Going by this figure of 65W per square metre - I would be looking at 13kW per hour though the night on fine days, but if we expect bad weather, we can light the fire in the dinning/lounge kitchen area and drop this to 3-5kW per hour in the bedrooms. 

So planning on 16 hours x 13Kw that is 208kw for overnight on fine days, or two winter days with the fire going.  We are setting up in-home childcare, so we need to heat most rooms for most of the day.   Where do I go from there in terms of Wattage of risers and size of tanks, as there are other factors such as

* how effective the radiators will be as the water cools  (what is the minimum temperature you would want your water to drop to?)
* How many days of cold water weather is it worth storing up (that is, how quickly will the tanks lose their heat naturally?)


1 month ago
A couple of years ago, we boiled quinces, (probably a few days later) put the juice in the shed fridge in jars and planned to make Quince jelly with it.  A few months later rediscovered the jars.  Some were rotten, but some had turned into the delicious mild fermented drink (?wine) that we had a little of on special occasions for the next year - I was raised teatotaller, did not taste alcohol till I was thirty, and probably drink about half a cup every year on average since then, so this wine was the exception.  The last quinces are falling off the tree here in New Zealand, and we would like to try repeating the experiment.  I can find no recipe that is just Quince Juice without all sorts of other additives.  I do know from bread-making, that if you put dough in the fridge then the yeast activity slows right down and the lactic / acetic acid forming bacteria can take over more.  Any knowledge of this in making fermented drinks?
3 months ago
I have been told that it is possible to stimulate a goat into milk without it having to kid.  I know humans can do this.  Anyone have any experience with goats? 

I have been reading up about building or making our own biogas plant.  It is presented as a steady stream of great fertiliser, but then I have read conflicting reports about its safety for humans and soil life.  Some say it is better than manure, but I also read the below from this website.

Has anyone researched this aspect?  We would not put human manure in it, and we could put animal or just greenwaste in our biogas generator.  This would reduce the microbes going back to humans, but what about the toxicity to soil life?

We have also read about the (lack of) efficiency of biogas on this website and have wondered if it is the best way to go.  We currently have the house and water heated with solar water panels and wood.  our current usage is about 10kW of power a day, most of which is cooking.  We plan to get solar and already have the inverter and batteries (we have this to run a food trailer at the markets) so really only need the PV panels and charger.  We thought it best to get rid of our cooking needs first, and then add the solar panels to cover the rest.  We are looking at building a covered picnic area with a rocket stove/oven/thermal mass against the house, but thought we would also have biogas for the quick "five minute" boil of the kettle, when you don't want to light the fire.  But is this reallty time effective, or would the time spent tending a 1000L IBC tank generator be more than that of lighting a stick fire to make a cup of coffee?  We already plan to have stored water for heat in the house, so it would be an easy thing to put the IBC tank in side a wooden tank and keep it at 28C or more.

We also have sufficient grass clippings with toxic leaves and weed scraps to keep a biogas generator feed on a regular basis.  (we are in a temperate climate with frost but no snow and grass growing slowly through winter). 

We also have heaps of manure that we do collect in the field but it seems to me that the best use of that would be to grow compost worms to feed back to the chickens, as it feed value for the biogas seems not worth the hassle of turning into a slurry and feeding in.


Apart from the gas, digesters also produce waste sludge and supernatant, the spent liquid of the original slurry. The waste is rich in plant nutrients, and it's often touted as a great organic fertiliser. Many of the resources listed below claim that.

However, the people who design biogas digestion systems are nearly always engineers, not biologists, and they tend to think chemicals are chemicals, as indeed they are, and these particular chemicals are indeed both nutrients and organic. But that doesn't make it a fertiliser — in fact it kills earthworms and wrecks the soil micro-life, which is the basis of soil fertility. This is what biologists say about it:

"Placement of E. foetida [manure worms] into sludge freshly removed from an anaerobic digester or in freshly-passed human excreta results in 100% mortality within a few hours." — From "Physicochemical Requirements in the Environment of the Earthworm Eisenia Foetida", by David L. Kaplan, Roy Hartenstein, Edward F. Neuhauser and Michael R. Malecki, Soil Biology and Soil Biochemistry, Vol. 12, pp 347-52, Pergamon Press, 1980.
Biogas digestion is an anaerobic process (no oxygen involved), unlike composting, which is aerobic (with oxygen). Compost gets hot, up to 60 deg C or more (140 deg F), biogas digesters don't get hot. Anaerobic digestion produces volatile fatty acids and volatile organic acids, both of which are phyto-toxins — plant poisons. Not what you want in your soil.

Add the sludge and supernatant to your compost pile. Biogas digestion makes the best sense when it's coupled with hot aerobic composting, then nothing will be wasted. Also, the heat in an active compost pile can be harnessed to produce a hot water supply, which means you can use the compost to keep the digester at working temperature during cold weather.

Another myth is that the digestion process kills off the pathogens in the manure (cow, pig, poultry and human manure are common feedstock for biogas digesters). Hot composting kills off pathogens reliably, when it's done right, but biogas digestion doesn't kill the pathogens in the manure.

"Indian biogas plants have short detention times. These are unlikely to destroy intestinal parasites, which are widely prevalent in rural areas of India. As a result, if the biogas sludge were used as a fertilizer, it would likely increase the spread of intestinal diseases." — From "Community Biogas Plants Supply Rural Energy and Water", UNDP

"Work I did and studied in the 1970s with 'dungas' production (anaerobic digestion) in South Africa and India showed that the drawback was the high concentration of pathogens in the resultant slurry. ... It's the pathogen problem that caused me to abandon this line of research as a viable source of alternative energy production and return to aerobic composting." — Walker Bennett, Organic Gardening Discussion List, 15 Oct 1999.
This isn't a problem as long as you're aware of it. Adding the sludge and supernatant to the compost pile will kill all pathogens.

If you're not in a position to make compost, flush the sludge and waste liquid down the toilet — let your municipal wastewater treatment facility handle it for you, that's what they do all the time.

If you keep poultry, there's a way to make better use of the sludge, though it doesn't need very much of it. See High-protein poultry feed from thin air

5 months ago
We have the IBC drum ready, and the cow manure breeding flies by the dozens (we are in a "hot" NZ summer) so we want be collecting manure and starting our methane midi as soon as possible. 

The question is where to put it.  Will it smell and for how far?  On the other hand, how far away can it be put and still pipe gas to the house to burn for cooking?

There might be a thread I can't find that already discusses all this.

5 months ago

We are wanting to make an outdoor track that is smooth enough that pre-school aged children and ride pedal bikes.  Is concrete our only option?   If so - what is the most sustainable way to make it so it uses minimal concrete?  We can get river sand for almost free (the additional cost of petrol to bring it home with us when we are going somewhere we would go anyway). 

7 months ago