Loading ...
Sorry, an error occurred while loading the content.

Re: [pfaf] re: tomatoes in greenhouses

Expand Messages
  • fran k
    Hi. Thats interesting about the embodied energy used for the production of the glass and other materials. You need to do the research for the electric solar
    Message 1 of 6 , Mar 3, 2011
    • 0 Attachment
      Hi. Thats interesting about the embodied energy used for the production of the glass and other materials.

      You need to do the research for the electric solar panels. Once the embodied energy was high, and people like David Holgren were critical of it, but now its from 1% to 5% of the output over the lifetime of the panels. But, do the research to see.

      Electricity is a valuable form of energy for specific uses for which no other energy form can directly be used, such as music and communications and low energy lighting.

      Unfortunately it is to the electric companies advantage for us to consume lots of it, and also we tend not to be aware that we need to distinguish it as special. So we use it for things that can be perfectly well served by wood charcoal etc.

      Id say one other possibility could be to open up the ground within the greenhouse, to allow the heat from within the earth to come up. I hear that the earth stays at a constant 10c a metre below the surface. But again this is more or less hearsay, so anyone interested would do well to do some research on it. Im going to. :) frank

      On Thu, 03 Mar 2011 15:00 GMT Jonathan Teller-Elsberg wrote:

      >Traveler in Thyme,
      >
      >Yes, you are right that the benefits of overwintering tomatoes in a heated
      >greenhouse are far outweighed by the problems of unnecessary use of energy.
      >But that assumes that the greenhouse exists only for the tomatoes. If a
      >person has determined that they want/need a (heated) greenhouse for whatever
      >reasons already, then putting some tomatoes into it doesn't much change the
      >energy balance. Still, the joy of a fresh tomato shouldn't overwhelm
      >someone's rational thinking and lead them to install an energy demanding
      >greenhouse just for that simple pleasure.
      >
      >John Willis,
      >
      >Having sort of defended greenhouses above, now I'll beg to differ with you
      >about the efficacy of solar systems to power heated greenhouses. A passive
      >solar greenhouse is great, of course, though it does entail the embodied
      >energy of the materials that construct it--sometimes really significant
      >amounts of energy. That goes both for greenhouses glazed in glass or in
      >polycarbonate. Polycarbonate is massively energy intensive to manufacture,
      >as, of course, is glass. So all greenhouses, even passive solar ones, should
      >be considered carefully before being installed to determine if they really
      >will be utilized intensively enough to make up for their energy "cost" (not
      >to mention their financial cost).
      >
      >PV panels only up the situation. The embodied energy in PV panels is
      >significant and I suspect that, on balance, I'd be better off in terms of
      >global warming gas emissions eating lettuce trucked from California to
      >Vermont all winter than to install PV panels for the purpose of powering a
      >greenhouse for my winter veggies. (As above, if the PV panels are being used
      >for other reasons already, and have the spare capacity to boost a
      >greenhouse's viability, then go for it. But PV expressly for powering a
      >greenhouse? I fear that's a dead weight loss for the planet when all is said
      >and done.)
      >
      >I hope I haven't sounded too didactic. Sometimes I get on a high horse when
      >I don't mean too.
      >
      >Best,
      >Jonathan
      >
      >--
      >"We have changed the world, and we wonder why things won't stay the same."
      >-Les Lanyon
    • Matthew Sleigh
      Crystal fusion heat, solar ponds etc. Some low tech, low energy ways of keeping greenhouses/plants from freezing, there are probably better examples of similar
      Message 2 of 6 , Mar 4, 2011
      • 0 Attachment
      • Jonathan Teller-Elsberg
        Another source of information is Darrel Frey s recent book, based on his many years of experience and experimentation in Pennsylvania, The Bioshelter Market
        Message 3 of 6 , Mar 4, 2011
        • 0 Attachment
          Another source of information is Darrel Frey's recent book, based on his many years of experience and experimentation in Pennsylvania, "The Bioshelter Market Garden." He's established a working permaculture commercial (small-scale) farm, and one of his key components is a passively heated greenhouse system utilizing both passive solar orientation/design, and incorporation of the waste heat from composting and chickens (maybe other animals as well) to keep the greenhouse warm enough to produce crops through  the winter. http://www.newsociety.com/bookid/4082

          And then, of course, there are the books from Eliot Coleman about his four-season harvesting in Maine (USDA zone 5). He's done quite well with unheated greenhouse and, in his most recent book, details his more recent use of "minimally heated" greenhouse -- that is, greenhouse that are heated only enough to prevent the temperature from falling below something like 34'F / 1.1'C. (His unheated greenhouses will get as low as the teens'F in the coldest weather, but he grows crops capable of withstanding those temps unharmed.) http://www.chelseagreen.com/bookstore/item/the_winter_harvest_handbook:paperback and the older but still relevant  http://www.chelseagreen.com/bookstore/item/fourseason_harvest/

          Other books and online resources also give info on this sort of thing.

          Jonathan

          >>>>>
          Hi there,

          Poultry and other living beings we share our farm/homestead spaces with may
          contribute heat to a greenhouse in winter.

          Peace and love.

          Steve.

          --
          "We have changed the world, and we wonder why things won't stay the same." -Les Lanyon
        • john willis
          No problem - your reply is great and gives much food for thought.John. To: pfaf@yahoogroups.com From: jelsberg@gmail.com Date: Thu, 3 Mar 2011 10:00:40 -0500
          Message 4 of 6 , Mar 4, 2011
          • 0 Attachment
            No problem - your reply is great and gives much food for thought.
            John.


            To: pfaf@yahoogroups.com
            From: jelsberg@...
            Date: Thu, 3 Mar 2011 10:00:40 -0500
            Subject: [pfaf] re: tomatoes in greenhouses

             
            Traveler in Thyme,

            Yes, you are right that the benefits of overwintering tomatoes in a heated greenhouse are far outweighed by the problems of unnecessary use of energy. But that assumes that the greenhouse exists only for the tomatoes. If a person has determined that they want/need a (heated) greenhouse for whatever reasons already, then putting some tomatoes into it doesn't much change the energy balance. Still, the joy of a fresh tomato shouldn't overwhelm someone's rational thinking and lead them to install an energy demanding greenhouse just for that simple pleasure.

            John Willis,

            Having sort of defended greenhouses above, now I'll beg to differ with you about the efficacy of solar systems to power heated greenhouses. A passive solar greenhouse is great, of course, though it does entail the embodied energy of the materials that construct it--sometimes really significant amounts of energy. That goes both for greenhouses glazed in glass or in polycarbonate. Polycarbonate is massively energy intensive to manufacture, as, of course, is glass. So all greenhouses, even passive solar ones, should be considered carefully before being installed to determine if they really will be utilized intensively enough to make up for their energy "cost" (not to mention their financial cost).

            PV panels only up the situation. The embodied energy in PV panels is significant and I suspect that, on balance, I'd be better off in terms of global warming gas emissions eating lettuce trucked from California to Vermont all winter than to install PV panels for the purpose of powering a greenhouse for my winter veggies. (As above, if the PV panels are being used for other reasons already, and have the spare capacity to boost a greenhouse's viability, then go for it. But PV expressly for powering a greenhouse? I fear that's a dead weight loss for the planet when all is said and done.)

            I hope I haven't sounded too didactic. Sometimes I get on a high horse when I don't mean too.

            Best,
            Jonathan

            --
            "We have changed the world, and we wonder why things won't stay the same." -Les Lanyon

          • Steve
            Jonathan, No real need to apologise for advising someone to do a thorough accounting of energy. Peace. ... Frank, My friend has geothermal heating already
            Message 5 of 6 , Mar 4, 2011
            • 0 Attachment
              Jonathan,
               
              No real need to apologise for advising someone to do a thorough accounting of energy.  Peace.
               
              ----------------------------
               
              Frank,
               
              My friend has geothermal heating already installed under his barn in Ontario, Canada.  Not the Arctic circle, I'll admit, but pretty chilly in winter.  Second-hand information this may be, but he's an ex-economist, and if he would invest his energy in it he's probably done the research. 
               
              I'm sure you'll still do your own research, but perhaps this is a little incentive.
               
              Also, Sepp Holzer of Austria has been doing cold-climate permaculture for decades, and uses the heat retaining capacity of rock in his design to provide warmth.  The sun shines on the rocks and they warm up, then they release the heat after the air cools in the evening.. this effectively extends the day's warmth and prevents frost in microclimates.
               
              Peace,
               
              Steve.
               


              --
              "All that is gold does not glitter,
              Not all those who wander are lost;
              The old that is strong does not wither,
              Deep roots are not reached by the frost.
              From the ashes a fire shall be woken,
              A light from the shadows shall spring;
              Renewed shall be blade that was broken,
              The crownless again shall be king."
              ~  J.R.R. Tolkien

            Your message has been successfully submitted and would be delivered to recipients shortly.