Posted on 11/06/2017 8:55:52 AM PST by Wonder Warthog
Plants grown in this 'smart' greenhouse fared as well or better than plants grown in conventional greenhouses.
The first crops of tomatoes and cucumbers grown inside electricity-generating solar greenhouses were as healthy as those raised in conventional greenhouses, signaling that "smart" greenhouses hold great promise for dual-use farming and renewable electricity production.
"We have demonstrated that 'smart greenhouses' can capture solar energy for electricity without reducing plant growth, which is pretty exciting," said Michael Loik, professor of environmental studies at the University of California, Santa Cruz, and lead author on a paper that appears in the current issue of the American Geophysical Union's journal Earth's Future.
Electricity-generating solar greenhouses utilize Wavelength-Selective Photovoltaic Systems (WSPVs), a novel technology that generates electricity more efficiently and at less cost than traditional photovoltaic systems. These greenhouses are outfitted with transparent roof panels embedded with a bright magenta luminescent dye that absorbs light and transfers energy to narrow photovoltaic strips, where electricity is produced. WSPVs absorb some of the blue and green wavelengths of light but let the rest through, allowing the plants to grow. WSPV technology was developed by coauthors Sue Carter and Glenn Alers, both professors of physics at UC Santa Cruz, who founded Soliculture in 2012 to bring the technology to market.
Loik's team monitored photosynthesis and fruit production across 20 varieties of tomatoes, cucumbers, lemons, limes, peppers, strawberries, and basil grown in magenta glasshouses at two locations on campus and one in Watsonville, California.
"Eighty percent of the plants weren't affected, while 20 percent actually grew better under the magenta windows," said Loik. Tomatoes and cucumbers are among the top greenhouse-produced crops worldwide, he said.
In additional experiments, small water savings were associated with tomato photosynthesis inside the magenta glasshouses. "Plants required 5 percent less water to grow the same amount as in more conventional glasshouses," he said.
"I thought the plants would grow more slowly, because it's darker under these pink panels. The color of the light makes it like being on the Red Planet," said Loik. "Plants are sensitive not just to the intensity of light but also to color. But it turns out the plants grow just as well."
Reducing the energy consumed by greenhouses has become a priority as the global use of greenhouses for food production has increased six-fold over the past 20 years to more than 9 million acres today--roughly twice the size of New Jersey, according to Loik. "It's big and getting bigger," he said. "Canada relies heavily on greenhouses for vegetable production, and their use is growing in China, too." Plastic greenhouses are becoming popular for small-scale commercial farming, as well as for household food production, he added.
Greenhouses use electricity to control temperature and power fans, lights, and other monitoring systems. "This technology has the potential to take greenhouses offline," said Loik, who specializes in climate change, plant physiology, water resources, and sustainable technologies. Cost per panel of WSPV technology is 65 cents per watt--about 40 percent less than the per-watt cost of traditional silicon-based photovoltaic cells.
"If greenhouses generate electricity on site, that reduces the need for an outside source, which helps lower greenhouse gas emissions even more," said Loik. "We're moving toward self-sustaining greenhouses."
Cool. All energy is solar, some just takes millions of years to be turned into a usable form. This one works instantaneously.
I’m willing to bet that whatever minimal gain there might be in using a “smart” greenhouse is probably outweighed by the environment cost of mining for, manufacturing and distributing this technology over time.
However, there was one solar produce factory in Puerto Rico...and it survived...not all of it but most of it. Obviously, a good idea for Puerto Rico.
Another interesting technology, the article as usual omitting critical info: what’s the cost & efficiency of the PV components? Selective conversion of wavelengths, transparent to others, is novel for some applications but significantly limits the energy extracted; not saying it’s not worthwhile, just that it has a specialized application that may or may not benefit cost-wise.
Remember: the absolute upper limit for solar power is 1300 watts per square meter; various factors (efficiency, conversion loss, etc) reduce the practical peak energy extraction to 130 W/m^2, with other factors (angle, night, clouds, etc) reducing average long-term collection down around 13 W/m^2. By further discarding visible light & other wavelengths, we’re down to maybe 1 W/m^2. If the greenhouse surface is 1000 m^2, maybe it’s just better to use regular PV on an adjacent 100m^2 space. (Back of napkin SWAGs here.)
Interesting, yes. Exploring options for expanding solar power collection is a good thing. Solid-state localized power production promotes self-sufficiency.
These are confined gardens. Normal gardens pour nutrients into the soils. Yes, you have to rotate but it’s a natural method.
So do NON-ELECTRIC solar green houses.
God had the idea first....
Sounds promising.
But do not give me tomatoes grown indoors. They just don’t have the flavor.
1) The amount of photovoltaic material required is confined to a thin strip around the outside of the rectangular panel. The collector area is much, much larger, but it is simply doped glass (or plastic). Such "edge cell" collectors have been done before.
2) The construction of the greenhouse absorbs the whole cost of the support structure and land for the photocells, and turns that investment from a "sunk" cost into a profit generator instead
The combination of the two offers the potential of reducing cost and increasing income of the total system. I like the "outside the box" thinking that is evidenced.
Yes, there are a lot of details that would be nice to have, but R&D mag is a technology survey focussed source, not one that offers exhaustive analysis.
That has more to do with the varieties planted than anything else. Years ago, an agronomist friend of my dad's tried raising greeenhouse tomatoes. His tasted as good as any grown fresh. And I am very much a tomato connoisseur.
Don’t tell any of them that “Plastic Greenhouses” are made from Petroleum.
Does appear to be efficient
Something important appears to be missing from that rather (intentionally?) imprecise statement.
If they have a process or technology that reduces the cost of "traditional silicon-based photovoltaic cells" (whatever that means - there are several different technologies that have traditionally been used to create silicon-based photovoltaic cells, from thin-film to polycrystalline to monocrystalline silicon and perhaps beyond, each of which has its own cost structure as well as pluses and minuses), then wouldn't that be expected to stand on its own and compete with those technologies, with nary a tomato in sight?
What are the negatives which somehow did not make it into that article? Increased size of the panels compared with "traditional" ones? Limits that affect these panels that do not affect "traditional" ones? Toxic fumes or radiation that they emit? Something else?
Was the article written as a press release? It does seem to be a bit of a 'puff piece', with the author's name hidden behind the byline of 'University of California, Santa Cruz'. The article quotes the lead author of a paper about this subject: Michael Loik, professor of environmental studies at the University of California, Santa Cruz, and also gives a shout-out to: "coauthors Sue Carter and Glenn Alers, both professors of physics at UC Santa Cruz, who founded Soliculture in 2012 to bring the technology to market."
So, it would not be surprising if the information presented in this article is, um, pretty worthless, or at least substantially oversold...
I think I addressed most of these in post 9). It is the combination that offers synergies that reduce the total cost per watt of installed capacity.
But do not give me tomatoes grown indoors. They just don’t have the flavor.
__________
I used to agree with that statement.
A few years ago, I set up a plastic greenhouse for container-grown tomatoes. I used a magenta screen cloth to add red light while actually shading my plants from the intense sunlight that was requiring too much watering and causing blossom end rot. My fruit (all varieties from Camparis grown from saved seed to beefsteaks, including a few heirlooms) did wonderfully. Intense, old-fashioned flavor. No BER. Earlier and later production. Bumper crops. I had sauce and dehydrated tomatoes from that year for 4 years after. I also worked myself way too hard preserving everything.
I have been a devotee of Camparis for years. I drive out of my way to the only nearby outlet that sells them. This past summer, I began purchasing tomatoes from a local organic commercial greenhouse operation. They had fantastic heirlooms (Berkley Tie-Dye) in early June! They had heirloom production, including a wonderful little oval green mini I don’t recall the name of, all season long. Their standard slicer was uniform, tasty and available in quantity before any other local grower and well into October.
I did purchase some beefsteaks, as well as 4th of July types for dehydrating, from traditional gardeners and they were wonderful, but I noticed the outdoor fruit risked being watery and did not keep as well as the greenhouse variety, as well as being more susceptible to pests. The same hybrids grown outdoors were only available in mid-late summer, were noticeably smaller (Berkley is usually small-fruited anyway) and had a 4-week season. The taste was identical to the greenhouse produce.
Commercial tomatoes are generally horrid, but it isn’t just because of greenhouse production. Varieties bred for transport are one of the main problems. The greenhouse I now swear by produces for four supermarkets and does 2-3 Farmer’s Markets/week. They start their plants in February and transplant in April for June maturity, staggering their plantings to insure product through until the end of October. Amazingly enough, while the outdoor varieties were predictably mealy after the nights began to cool into the fifties, the greenhouse product remained as palatable as mid-summer produce. Oh, and they had sweet red peppers a couple weeks or more before anyone else in the area.
It can be done.
OK, except that the cost per watt figure that they quote does not sound like an installed capacity cost, rather it is more likely to be a cost for panels alone.
It does appear to be a poorly-written article, but then again, maybe the raison d'être of R&D Magazine is merely to spark interest in a subject by publishing more in the way of marketing-oriented fluff than actual substance, with the understanding that interested readers can follow up elsewhere to learn the details.
I've subscribed to R&D mag for a VERY long time, and you are right that the overall article quality has gone down...but what in journalism hasn't done the same in recent years. I've castigated some articles in their comments myself. But this particular idea I felt was sufficiently innovative to pass on.
Fluorescence-doped transparent sheets with a bonded-on photovoltaic strip along the edges were originally developed to take shorter-wavelength photons (most of incoming solar radiation), and through absorption and fluorescence processes in the dopant, shift the overall photon flux into longer wavelength photons which were a more efficient match for the conversion spectrum of silicon photocells.
Doing all of that and still passing the photons that plants need is a nice tweak.
Ah, a fellow tomato lover! Vine-ripened beefsteak tomatoes from “mah mama’s” garden in South Louisiana. One slice of tomato covering a whole slice of bread.Who needed bacon??
Nirvana!
Thank you for all of that information.
Do you mind telling me what state you are in? I live in Maryland.
Yes, I know about the grocery store tomatoes. The same is true of apples.
A nearby small town has a farmers’ market on Saturday mornings. Last year, in November, I was surprised to see that one of the stands had tomatoes. In the past, I have bought wonderful tomatoes from these people. They told me that they had grown these tomatoes in the greenhouse. They were just beautiful but tasteless.
Admittedly, this is just one case that I have experienced. So I will keep an open mind and think about exploring some other indoor production sites in the area.
Thanks again.
Okay, thanks.
I’m in SW WI.
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