Showing posts with label solar cells. Show all posts
Showing posts with label solar cells. Show all posts

Friday, October 31, 2008

Dr. Gideon Polya on End of Coal Power

Dr Gideon Polya makes and documents the very good point that alternative energy strategies are converging in cost and price with the established fossil fuel protocols. All these systems had the potential to do this or they would simply not have been pursued in the first place. That thirty years of development and research effort is visibly paying of is gratifying.

Dr Gideon Polya is an apologist for a fair bit of left of center political thinking, but he has come through here with a tidy bit of home work on the developing trends in alternative energy systems.

The most visible at present are the now thousands of windmills built and been built. They are easily on the way to providing ten percent of global grid power. Further technical progress such as the axial motor promises to add a couple of points there and the addition of vanadium redox batteries can expand its usage as a sole source power system for large industrial installations. These ideas are all possible because it is simply becoming price competitive.

Cheap solar installations are also soon to become very visible and the same comments apply.

Tide and wave are still at the stage that windmill power was at thirty years ago and we will be waiting those thirty years before it may become important.

All these systems needed some form of non consumable energy storage. That is becoming available with the emergence of vanadium redox batteries.

What is important in this presentation is that all this is now becoming directly competitive with coal fired power plants. Bluntly put, coal is now on the road to extinction and it will happen over a generation at most. The coal industry was preserved as a power source solely because of price and easy availability. Windmills are even more available because of both modular design and much less stringent permitting needs. The same will hold true for cheap solar now coming on stream.

I could find no way to link the art work, but you may go to this link to see it.

http://mwcnews.net/content/view/26137&Itemid=1

“One Day Pathétique” Symphony Painting

Tchaikovski’s final “Pathétique” Symphony is actually Joyous and Hopeful as is the energy cost cross-over point - the best renewable and geothermal power options now cost the same as coal power.

I have painted a huge (1.3 metre x 2.9 metre) painting entitled “One Day Pathétique” that captures Pyotr Ilyich Tchaikovski’s final Symphony Number 6, the so-called “Pathétique”. Tchaikovski was delighted with this symphony but because he died a fortnight after its first performance the symphony has become known as the “Pathétique”. There is, however, a joyous and hopeful interpretation of this great work as opposed to the traditional sad, pathos-laden view. One Christmas morning I listened to Tchaikovski’s Symphony Number 6 as the sun was rising over the beautiful Yarra River Valley and I suddenly realized why Tchaikovski was so pleased with his final symphony – it clearly describes one day in the life of a human being. The Symphony is in 4 Movements and is famous for starting off very gently (as one slowly wakes up) and for concluding so softly that you strain to hear the last notes (as one drifts off to sleep after a full day). In between, the Symphony successively evokes the early morning, morning activities, noon time glory, the march of shadows in the late afternoon, and the glory of the stars. Once you realize the One Day interpretation everything fits so beautifully that you can really understand why Tchaikovski was so delighted with the symphony and regarded it as his finest work.

My “One Day Pathétique” Symphony Painting is also conveniently divided into 4 Sections (evoking the 4 Movements of the Symphony) which are determined by the 4 major overlapping circles of a classical Italian Renaissance Double Golden Rectangle geometry. I use beautiful young maidens as figurative, almost abstract expressionist elements to tell the story of a lovely day. Reading Left to Right, the maidens slowly wake up (as do birds and flower buds); they then go into the woods gathering wood, berries and flowers; midday sees them busily engaged in the meadows (as are rabbits and birds); and in the evening the glorious stars come out, the birds roost, night birds fly out to hunt, and the maidens rest and finally drift off to sleep.

My “One Day Pathétique” Symphony Painting is about joy, beauty, nature and hope – and is ideal for illustrating the Good News in the current Climate Emergency. Just as my painting was inspired by the Sun coming up over the beautiful Yarra Valley, so have I been galvanized by our local Yarra Valley Climate Action Group that is trying to help save the Planet from man-made global warming. Many of my colleagues in the Yarra Valley Climate Action Group (and in its umbrella Climate Emergency Network and Climate Movement national umbrella groups) are deeply despondent about the notorious Australian inaction in the mounting Climate Emergency. Australia is the world’s biggest coal exporter and one of the world’s worst per capita greenhouse gas polluters but its extreme right wing, pro-Coal Government is strong on rhetoric but lacking in action. The $100 billion per annum Australian coal industry has effectively squashed sensible action and determined the resolutely pro-Coal stance of the major political parties (the Federally-governing Labor and the Opposition Liberal-National Party Coalition, these being collectively known as Lib-Labs). I am nevertheless optimistic and tell my colleagues that science, technology, sensible risk management and sensible business practice will eventually triumph over neocon greed, irresponsibility, denial, ignoring, climate scepticism, climate racism, climate terrorism, climate genocide, dishonesty and spin.

Man-made (anthropogenic) greenhouse gas (GHG) pollution from fossil fuel burning, methanogenic livestock production, other agriculture (notably major crop-based biofuel generation) and deforestation have lifted the atmospheric GHG concentration to a dangerous level. Top US climate scientist Dr James Hansen (Director, NASA Goddard Institute for Space Studies) has declared that “If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted, paleoclimate evidence and ongoing climate change suggest that CO2 will need to be reduced from its current 385 ppm to at most 350 ppm (see:
here ), a view recently essentially endorsed by the Head of the Nobel Prize-winning UN IPCC, Dr Rajendra Pachauri.

In 2007 I published an assessment of the relative costs of power from a variety of sources (see:
here ). A key observation was that a Canadian Ontario Government-commissioned study had found that the “true cost” of coal burning-based power (taking the human and environmental impact into account) was 4-5 times the “market price”. Already in 2007 it was apparent that the cost of power from all the lower-cost renewable energy systems (in cents per kilowatt hour) was LOWER than the “true cost” coal burning-based power.

However, as summarized below, it is now apparent that a crucial CROSS-OVER POINT has now been reached at which the cost of power from a range of lower-cost renewable sources is about the SAME as the “market price” of coal burning –based power. In the analysis below the COST OF POWER (e.g. as measured in units such as US cents per kilowatt hour or US$ per megawatt hour) is given for a variety of non-carbon energy sources, together with an estimate of the MAGNITUDE of the various renewable and/or non-carbon energy resources. For detailed documentation of the information given below the reader is directed to a summary provided (with numerous links) by the Yarra Valley Climate Action Group entitled “
CROSS-OVER POINT: Best Renewable and Geothermal Power NOW for SAME COST as Fossil fuel-based Power”.

1. Wind Power

According to NOVA Science in the News (published by the prestigious Australian Academy of Science, 2008): “advances in wind power science and technology are reducing the cost of wind power to a point at which it is becoming competitive with many other energy sources (at about 8 Australian cents per kilowatt hour)” [i.e. 5.6 US cents per kilowatt hour [kWh] or US$56 per megawatt hour [MWh]). According to the British Wind Energy Association (BWEA) the average cost of onshore wind power in the UK (2005) was 3.2 p/kWh [i.e. 5.2 US cents per kilowatt hour or US$52 per megawatt hour (MWh)] . According to the US Energy Information Administration the cost per unit of energy produced from wind was estimated in 2006 to be comparable to the cost of new generating capacity in the United States for coal and natural gas: wind cost was estimated at US$55.80 per MWh [megawatt hour], coal at US$53.10 per MWh and natural gas at US$52.50 per MWh.

According to a Stanford University study “global wind power generated at locations with mean annual wind speeds ≥ 6.9 m/s at 80 m is found to be ~72 TW (~54,000 Mtoe [million tons of oil equivalent]) for the year 2000. Even if only ~20% of this power could be captured, it could satisfy 100% of the world’s energy demand for all purposes (6995-10177 Mtoe) and over seven times the world’s electricity needs (1.6-1.8 TW)”.

There is huge potential for off-shore wind power. According to Research and Markets (May 2008; summarizing the Global Wind Power Report 2008): “Wind is the world’s fastest-growing energy source with an average annual growth rate of 29% over the last ten years. In 2007, the global wind power generating capacity crossed 94 gigawatts (GW). This represents a twelve-fold increase from a decade ago, when world wind-generating capacity stood at just over 7.6 gigawatts (GW). Being an emerging fuel source a decade ago, wind energy has grown rapidly into a mature and booming global industry. Further, the power generation costs of wind energy have fallen by 50%, moving closer to the cost of conventional energy sources. The future prospects of the global wind industry are very encouraging and it is estimated to grow by more than 70% over the next five years to reach 160 gigawatts (GW) by year 2012”.

2. Concentrated Solar Power with Energy Storage

The US solar energy company Ausra uses a form of Concentrated Solar Thermal (CST) technology called Compact Linear Fresnel Reflector (CLFR) technology. In short, solar energy is collected and concentrated in a sophisticated way and used to generate steam to drive turbines and hence generate electricity. A key feature is that solar energy is stored, enabling Ausra CLFR plants to generate electricity 24 hours per day. An Ausra factory producing 700 megawatt (MW) of solar collectors annually opened in Nevada in 2008. Ausra is involved in joint construction of a 177 megawatt (MW) CLFR plant for California. According to Ausra (2008): “Ausra's innovations in collector design dramatically reduce the cost of solar thermal generation equipment and bring solar power to prices directly competitive with fossil fuel power. Using Ausra's current solar technologies, all U.S. electric power, day and night, can be generated using a land area smaller than 92 by 92 miles”.

Solar energy hitting the Earth is roughly 10,000 times greater than the energy we consume globally. Global electricity production (2005) was 17,400 TWh. Exciting new research developments on hydrogen fuel cells (at Monash University, Australia) and efficient electrolysis (at the Massachusetts Institute of Technology) presage an efficient, solar energy-based, hydrogen fuel cell-run transportation system within a decade.

3. Wave power

The cost of wave power by the CETO system (a sea bed-fixed pump linked to a buoyant actuator) is about that of wind power. There are further big cost efficiencies if wave power is used for cogeneration of potable water. A Carnegie Corporation submission to an Australian Parliamentary Committee (2007) states: that “CETO can offer zero-emission base-load electricity generation capacity at a cost comparable to existing wind power [i.e. about US$50 per MWh] and the capacity to provide potable water to major population centres using 100% clean energy”.

Further, this Submission states: “The World Energy Council has estimated that approximately 2 Terawatts (TW), about double current world electricity production, could be produced from oceans via wave power … It is estimated that 1 million gigawatt hours (GWh) of wave energy hits Australian shores annually, or more than four times Australian’s total annual electricity consumption of 210,000 gigawatt hours (2004 figures)”.

4. Hydro power

According to the New Zealand Ministry of Economic Development (2002) various New Zealand hydroelectric power systems provided power for 4-10 NZ cents per kilowatt hour [2.4-5.9 US cents per kilowatt hour i.e. US$24-59 per megawatt hour].

According to BNET (2007): “Hydropower currently accounts for approximately 20% of the world's electricity production, with about 650,000 MW (650 GW) installed and approximately 135,000 MW (135 GW) under construction or in the final planning stages … It is estimated that only about a quarter of the economically exploitable water resources has been developed to date”.

5. Geothermal power

According to Professor John Veevers (Department of Earth and Planetary Sciences, Macquarie University, Sydney, Australia): “The [Australian hot rocks] geothermal resource extends over 1000 square kilometres … Modelled costs are 4 Australian cents per kilowatt hour, plus half to 1 cent for transmission to grid [4.5 Australian cents per kWh = 3.2 US cents per kWh or US$32 per MWh]. This compares with 3.5 cents for black coal, 4 cents for brown coal, 4.2 cents for gas, but all with uncosted emissions. Clean coal, the futuristic technology of coal gasification combined with CO2 sequestration or burial, yet to be demonstrated, comes in at 6.5 cents, and solar and wind power at 8 cents” see “The Innamincka hot fractured rock project” in “Lies, Deep Fries & Statistics”, editor Robyn Williams, ABC Books, Sydney, 2007; also see energy cost-related chapters in this book by Dr Gideon Polya “Australian complicity in Iraq mass mortality”, Dr Mark Diesendorf “A sustainable energy future for Australia”, and by Martin Mahy “Hydrogen Minibuses”).

According to the Report of an interdisciplinary panel of Massachusetts Institute of Technology (MIT) experts entitled “The Future of Geothermal Energy” (2006) : “EGS [Enhanced Geothermal Systems] is one of the few renewable energy resources that can provide continuous base-load power with minimal visual and other environmental impacts … The accessible geothermal resource, based on existing extractive technology, is large and contained in a continuum of grades ranging from today’s hydrothermal, convective systems through high- and mid-grade EGS resources located primarily in the western United States) to the very large, conduction-dominated contributions in the deep basement and sedimentary rock formations throughout the country. By evaluating an extensive database of bottom-hole temperature and regional geologic data (rock types, stress level, surface temperature etc), we have estimated that the total EGS resource has to be more than 13 million exajoules (EJ) [13 million EJ x 277.8 TWh per EJ = 3611.4 million TWh]. Using reasonable assumptions regarding how heat would be used from stimulated EGS reservoirs, we also estimated the extractable portion to exceed 0.2 million EJ (0.2 million EJ x 277.8 TWh per EJ = 55.56 million TWh) ... With technological improvements, the economically extractable amount of useful energy could increase by a factor of 10 or more, thus making EGS sustainable for centuries” (see Chapter1, p1-4).

Nuclear power can be dismissed as a serious future option in this analysis because the overall nuclear power cycle (from mining to waste disposal) currently has a major CO2-polluting component (equivalent to that of a modern gas-fired power plant); the cost of nuclear power via the UK's newest Sizewell B plant is 15 Australian cents per kilowatt hour [10.5 US cents per kilowatt hour or US$105 per MWh; required high grade uranium ore is a very limited resource; and long-term safe storage of waste and security issues are unresolved. Biofuel from land-based crops (notably canola, palm oil, sugar and corn) is highly CO2 polluting from mechanisms such as de-forestation and loss of soil carbon. Indeed the biofuel perversion that is legislatively mandated in the US, the UK and the EU is making a huge contribution to global food price rises that in turn are threatening the lives of “billions” of people according to UK Chief Scientific Advisor Professor John Beddington FRS (see “Global Food Crisis. US Biofuel & CO2 threaten billions”:
http://mwcnews.net/content/view/21277/42/ ).

In Summary, while the World has arguably already reached “peak oil” and uranium, gas and coal resources are limited, the solar energy hitting the Earth is roughly 10,000 times greater than the energy that Man consumes globally. Geothermal resources are immense. Already developed and implemented geothermal power technologies and low-cost renewable energy technologies directly dependent on solar energy (concentrated solar thermal power) or indirectly dependent on solar energy (hydro, wind and wave power) have reached a CROSS-OVER POINT at which the cost of power in cents per kilowatt hour are COMMENSURATE with the current “market cost” of fossil fuel burning –based power. Further, the “true cost” of coal burning-based power (i.e. taking the environmental and human impact into account) is 4-5 times the “market cost”. Exciting new research developments at Monash University, Australia, and at the Massachusetts Institute of Technology, USA, presage the possibility of an efficient, solar energy-based, hydrogen fuel cell-run transportation system within a decade.

Former US Vice President and Nobel Laureate Al Gore has recently (mid-2008) called for 100% renewable electric power with ten years: “Today I challenge our nation to commit to producing 100 percent of our electricity from renewable energy and truly clean carbon-free sources within 10 years” (see:
here). Carbon-free power is now technically and economically feasible at a “market cost” commensurate with the “market cost” of fossil fuel burning-based power.

The science, technology and economics thus indicate that the urgent need (enunciated by NASA’s Dr James Hansen and his colleagues) to reduce atmospheric CO2 concentration from the current 387 ppm to no more than 350 ppm can be realized NOW with low-cost renewable energy and geothermal energy implementation coupled with cessation of fossil fuel burning and de-forestation, minimization of agricultural methanogenesis, massive re-afforestation and return of carbon as biochar to the world’s soils.

Just as there is an Optimistic Interpretation of Tchaikovski’s “Pathétique” Symphony, so we see that with honesty and goodwill the World can successfully address the acutely serious Climate Emergency in a vigorous and timely fashion.

Dr Gideon Polya, MWC News Chief political editor, published some 130 works in a 4 decade scientific career, most recently a huge pharmacological reference text "Biochemical Targets of Plant Bioactive Compounds" (CRC Press/Taylor & Francis, New York & London, 2003), and is currently writing a book on global mortality ---

Thursday, January 3, 2008

Industrial Solar Cells and Scientific American

Scientific American has an article out on Solar cell technology this month. I actually found it a bit disappointing. Very much about engineering solutions with the tools at hand and all the problems with distributed power production and transmission over distance that has haunted the electrical industry from its inception.

A lot is made of solar cell arrays and the idea of huge array farms. A good bit of information is that new technology is now raising the efficiency bar to over 10% for field operations from a prior level of around 7%. A lot is also made of using mirrors to heat a working fluid to drive turbines. This is all good classic thinking that was stillborn last time around by the sheer weight of capital costs and obvious transmission losses from the deserts to the customers.

It is still good stuff and will appeal to the large budget boys. It may even make money.

One aspect of all solar systems that I have never seen anyone allude to is the problem of wind blown silica dust abrasion in the deserts. This is not a problem in any less hostile environments but will be a monster in the best locales. Any thing that can strip the finish of a car in a year will wreak even glass in the same time frame.

I would like to see an article that addresses that issue. I would hate to think that all those new shiny solar farms will be turning into a promoter's nightmare in a year or two. Perhaps my years of listening to dream spinners has made me a little too sceptical.

Right now, we can be very selective in our positioning of farms. That will end pretty quickly when it is decided to build out thousands of acres. I only hope that the taxpayer does not get handed the bill.

Recently, Hydro Quebec mothballed a brand new gas plant because their market projections failed to materialize. What were they thinking? They should know their potential market to a percentage point. Which means that studies were commissioned until someone gave them what someone wanted to hear. And now his successors are eating it. And this from a company that has the best power resource that you can imagine.

The main thrust of the article is to show, however implemented, that solar energy is there for the taking and that is can displace all our static energy needs and perhaps a lot of our transportation needs. The engineering fixes described are not very convincing as yet, but this does focus attention on the fact that we have an alternative for a price that is amply sufficient.

If we are using solar shingles in the next decade with an efficiency of 15% at acceptable cost, then that is likely more than good enough. And everyone of us can help make that happen.

Thursday, October 11, 2007

Nuclear Future

As my readers know, I do not lose much sleep over any likely shortage of grid power anytime soon. There is just too many ways to improve utilization and to produce this power load. Surprisingly, the least costly source of new power available to us will continue to be nuclear, provided we continue our perfection of process.

Fear of something has crippled the industry for thirty years. Yet the industry needs only to advance the engineering a little to make the technology bullet proof, permitting containable accidents only.

More importantly, the advent of breeder reactors will allow fuel to be reprocessed and essentially reused until the uranium itself is fully consumed. This will eliminate the spent fuel storage problem. (which is why the utilities keep the stuff) It is just that this whole cycle will take many decades to totally implement, but we will get there.

Again we have to struggle with the public relations problem presented by plutonium. And again the security protocols must be bullet proof. Engineering can do this.

We are now expecting a three fold increase in nuclear plants to take the place of non existent hydro plants. This inventory should be sufficient for the globe with additional grid power needs fulfilled by the range of alternates.

These alternates properly include volcanic geothermal. a little hydro,wind and tidal, and a lot of fossil fuel for decades to come.

I do not think that solar will ever be a good choice for grid power. It really wants to be operated off grid because of the space requirement. It really shines on the roof of a building suppling that building. On the other hand, it may become so much in surplus that we have to feed it into the grid.

My own sympathies are to take the excess solar energy and use it to harvest atmospheric water for the local trees. This will be a great choice in most places except the occasional rain forest.

My real point is that the advance of technology will put us in an ocean of electrical energy. Imagine the Sahara desert totally forested and watered through stand alone solar panel driven water collectors. The surpluses would be unbelievable. To say nothing of the likely surplus of water that will build up and develop drainages. Recall that the Sahara used to be covered with large lakes.

The difficulty is that electricity does not transport very well. It was the increase in transmission distances by several hundred miles that permitted the development of James Bay in Quebec. Any protocol that could eliminate the transmission by wire system we have with a truck friendly containment system would be a revolution in energy and would at least double our current available energy supply. It would also lead to a possible fix in transportation energy.

Right now, it is a possibility in theory only, with the implementing technology still too undeveloped. And if biodiesel from algae pans out, we will never really need to go there except as an intellectual exercise.



Tuesday, October 2, 2007

Solar revolution slowly unfolding

One aspect of the energy industry that has almost been forgotten in the hoopla over nascent technologies, is the progressive maturing of the solar energy industry. It is now the one sector that can turn on a dime with the advent of technology breakthroughs. They can manufacture panels as mechanically efficient as possible and install them as cheaply as possible. They have the needed gadgets to exploit the production energy. It has all been invented and perfected over the past thirty years.

Current manufacturing is dominated by companies in Japan and Europe. And in spite of the raw cost , it has found multiple markets and has become a large well funded industry.

This has resulted in a progressive improvement in the efficiency of silica based systems which remains largely the dominant technique.

It is still a niche solution, but it is a large industry in spite of all that. It is amazing what twenty years or so of hard work will do.

What I am waiting for is the implementation of printed solar cells on a plastic substrate that achieves 30% efficiency using nano-scaled structures. That will crash the cost of the active component by an order of magnitude and bring solar energy fully into the mainstream.

That level of cost reduction will make every building on earth potentially grid free. The industrial infrastructure is already in place to do this.

The other big gain for planet earth, as I have posted before, is that this will be cheap enough to produce a stand alone atmospheric water collector that can support the covering of the deserts with trees. It becomes the terraforming machine.

I also suspect that we will all live to see this energy revolution happen .

Monday, July 23, 2007

Interim Technology for Athmospheric Water Harvesting

I have described the several components necessary to establish successful stand alone water harvesting. In my drive to emphasize the stand alone aspect, we have ignored the possibility of a making a plug in device to harvest water for growing a tree in the back yard.

This would hugely benefit the urban landscape in the South West and California were water is not available yet a large tree in every backyard would actually help reduce air conditioning needs. I would be surprised if it actually balanced out but at least part of the cost of supporting the tree may be offset.

More importantly, perfecting a plug in device will perfect that part of the technology for the day that solar power is cheap enough. And it is a technology that everybody has understood for 100 years, yet resists perfection. So the more development we can do now, the better.

Besides a homeowner in Palm Springs will and can pay $2,000 for a state of the art water machine that allows him to grow a large shade tree.

Wednesday, July 18, 2007

Terraforming - 2 - Arid Non agricultural lands

We have learned that a working agricultural soil can hold around 3500 cubic feet of charcoal per acre very easily. Also, over the centuries we can expect the soil bed to become progressively thicker, removing a lot of carbon below the cropping zone. at least that seems to be what happened in the Amazon.

We are obviously anticipating that this system can be applied to all cropland worldwide and I see little reason to think otherwise. The Amazonian proof is simply too compelling.

The remaining challenge is how to upgrade the status of dry lands currently unable to support agriculture. For every acre of farmland today, we have a matching acre at least of very attractive land that just needs a little water.

We can likely exclude dry grasslands from this quest, because the application of good husbandry will rebuild deep carbon containing soils with little human intervention. The buffalo commons is a great example. As is Central Asia. The only thing that is needed is the judicious use of barb wire.

Which leaves us with the deserts and the near deserts. In my earlier work I described a watering protocol that can make these lands totally accessible. to agricultural practice. It essentially envisaged a solar driven atmospheric water collector that primarily watered an adjacent tree eliminating the majority of any connective infrastructure.

It also made the technical component a simple manufacturing package not too unlike the manufacture of a car. Every part can be progressively be optimized and step by step be brought down in cost. My target cost for a 100 lifer per day device was well under $1000 sooner rather than later. Today a cobbled together package from off the shelf parts would likely be around $10,000. We have a ways to go.

The advantages are huge though.

1 A stand alone unit would require almost no maintenance or care and can be expected to run on automatic.

2 The water supply is continuous rather than sporadic. This means that surpluses will quickly build up and be identified, allowing diversion ultimately into smaller lower areas that can be intensely worked. The surplus can be expected to ultimately recharge the natural water table leading to the establishment of a natural hydrology.

3 The growth of the trees will provide shade leading to a significant drop in local temperature leading to more natural precipitation. Most of the water used daily by the trees will be re expelled into the atmosphere maintaining the natural humidity. This permits the envelop of humid air to be progressively extended into the desert opening up more land.

4 As the woodland is established, ground cover will arise allowing the husbandry of ruminants and the slow reestablishment of a living soil.

5 The farm will also be farming a surplus of direct electrical power and water. This surplus can be used to support other agricultural activities as may be feasible.


The coverage of huge acreages with this type of technical solution can be used to absorb a lot of the solar energy hitting the tropics and semi tropics and could lead to significant cooling. Most of the energy would be absorbed by the trees of course.