Thursday, November 30, 2006

Stirling Engines and Photovoltaics

One big advantage of systems that use Stirling Engines have over Photovoltaics is that many Stirling based systems have a battery built into the basic design. For example High Temperature Helostat and Dish systems use a salt-graphite mass at their focus as the hot-end block of their Stirling Engines. The mass behaves as a thermal battery

The state change temperature of salt from solid to liquid (molten) is 900 C. Like any solid to liquid state change, it absorbs a great amounts of energy. The physics of salt means that salt behaves in a constant desirable way between 600 C to 1500C. The thermal battery is heated by solar input during the day. Overnight, the Stirling Engine continues to draws off heat energy and generate power. The thermal battery's internal temperature falls accordingly. The follow days solar input reheats the salt graphite mass.

So these kinds of Stirling designs are potentially more cost effective for base load applications than Photovoltaics and Wind.


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Thursday, November 09, 2006

A Complete Food Chain and the 12 Permaculture Design Principles

There is an interesting post over on Backyard Aquaponics. It's called Complete Food Chain

In the thread Daniel wrote two posts;

once i have quarantined my shrimp long enough to go into the tank with the fish, i could probably achieve this, but only with a very small stocking density of fish.
Farming fish in farm dams extensively rely on this, and they fertilise their ponds before adding fish to increase algae growth, which in turn supports more microorganisms, and so on


wait, if i did what was mentioned in my post above, i couldn't have any plants growing aquaponically with only an input of CO2 and sunlight

well i have confused myself, i have a feeling that there would need to be an input of fish food/nutrients to grow plants aquaponically as well

ah well someone else probably has some more helpful insight, and i will check this topic with eagerness to see if its possible

I'd like to add two comments about Daniels posts.

Firstly, about fish growers fertilizing their dams to increase algae & intermediate organisms before adding fish. This fertilizer is effectively embodied fossil fuel energy. In the systems we are trying to build, we can do these kinda things, but the way we do them means the scale will differ. Our processes will require more labour, land/water area, time and/or capital/materiels so that we can embody solar energy. We can play with the mix, but it won't be the fast easy fix of cheap fossil fuels.

Secondly, Daniel commented about growing algae precluded growing plants aquaponically. True, but another way to think of it, is that the fish components of the system produces a certain amount of nitrogen. It's your decision as the designer/maintainer to determine how much of the nitrogen flow goes to plant production (for human/animal use) and how much goes to algae production (for internal system feed stocks).

After I made my initial post, I was looking for a better way to express additional idea threads.

Then I hit upon the idea of using David Holmgren's 12 design principles as a lens.

  1. Observe and interact


  2. Catch and store energy

    Developing a system that captures and stores solar energy in usable/valuable forms

  3. Obtain a yield

    Developing a system that captures and stores carbon, nitrogen etc as high nutrition food stuffs

  4. Apply self-regulation and accept feedback

    Using large ponds, with caged off sub ponds and 'side' ponds to for produce feed stocks for the main fish speices. Thus using some of the nitrogen produced by the fish stocks to produce their own feed stocks. The system can also comsume excess output of Terrestial systems.

  5. Use and value renewable resources and services

    Produce high omega-3 fish meats, with commerial value.

  6. Produce no waste

    Using food stuffs that are in excess (roosters) as a feed stocks for a system that produces food stuffs that are in limited supply (omega-3 rich meats)

  7. Design from patterns to details


  8. Integrate rather than segregate

    Meshing the aquaponic system design with terrrestral systems.

  9. Use small and slow solutions

    Use many sub pond and 'side' ponds rather than a small number of large ponds.

  10. Use and value diversity

    Using many feed stock source to ensure more stable system dynamics.

  11. Use edges and value the marginal

    Ulitize and manipulate pond surface & pond walls/floor to increase cumclative total production.

  12. Creatively use and respond to change


Is it time to draw a mind map?


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Monday, November 06, 2006

Water for the Cities

While down south, I also heard that there are purposals to devert water from the Waranga Mallee channel (at Colbinabbin) to the City of Bendigo and possibaly to the City of Ballarat.

Note that Ballarat is on the south side of the Great Dividing Range water shed. So water would be being diverted from the inland to the coastal margins.

I would think that the value of the uses of this extra water would justify some solar desalination research.

See Landline and Pyramil Salt


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Sunday, November 05, 2006

An old teachers view of the drought

I've been away during the last 10 days. Down south in Melbourne.

Yesterday I was talking to a retired school teacher. He taught in a number of country schools in his younger days.

His commented about this winter's drought was that Melbourne was getting Bendigo's weather and the Bendigo was getting Mildura's weather. That the rain in Melbourne this winter would be just about right for a wheat crop, where normally it would be too wet.

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