Storing the sun

Filed under: Alternative/Green Building |

by Nicholas Chambers

In speaking of such feats as storing the sun, we are also discussing methods to bottle wind, yoke water, or cruciblize earth. Accessing the sun’s energy when it is not shining is a matter of modern alchemy—of tapping into the other living and elemental facets of nature. We all owe our existence to the irradiant grace of our nearby star; some of us inherently utilize it more directly than others. Biomass, for instance, is really but a stored, solar-energy depository within a continuum of broad biological and atmospheric cycles. Air can also be pressurized in caverns, and water pumped to elevation or electrolyzed into hydrogen, all with the energy from the sun.  As the classical axiom says: energy is neither created nor destroyed; only transformed.

The carbon cycle

The entirety of photosynthesizing nature (mostly plants), grossly labeled biomass, has been in the business of banking solar energy for millennia.  While only operating at 1-2 percent efficiency, the plants and algae of the earth are capable of storing an estimated 80-100 terawatts of energy per year. That’s roughly seven times the yearly consumptive habit of humanity. Not only do they store the sun’s energy by propagating themselves year after year, they also carry on one of the most important cycles of the earth: the carbon cycle.

Photosynthesis extracts carbon from the atmosphere (in its gaseous form, CO2) to build up organic matter/plant tissue and release oxygen as a by-product.  Earth’s atmosphere with 20 percent oxygen, fortunately for us, is due to this very process.  As those plants decay, their carbon is again released as CO2 and the loop continues.  In contrast, fossil-fuel carbon hasn’t been in our atmosphere for over 65 million years, thus far exceeding the carbon uptake capability of the biosphere!

The solar energy that becomes sequestered in plants is dispersed throughout the whole food chain, feeding larger herbivores and carnivores, not to mention producing the heat from the wood or pellet stoves in our homes.  Similarly, the metabolic flame that burns inside horses on a cold winter night is nothing other than a relic of sunshine stored in the grass hay that grew the previous summer.  Or as a Greg Brown poem speaks of canned fruits and vegetables in the winter: there’s “summer in a jar!”

The value of recognizing biomass as stored solar energy is that it can be a strategic complement to the evolving energy landscape happening in the San Luis Valley and around the nation.  The fact is that the sun doesn’t always shine nor the wind blow, and night happens every day, yet our consumptive habits have calloused into uninterrupted usage despite the rhythm of the sun and wind.  If coal is not going to be the only baseline (24 hours a day, 7 days a week) electricity provider for the future, then there are needs for renewable, clean, value- and job-producing industries that will.

Woody biomass

With the epidemic of beetle kill timber throughout Colorado and much of the west, there is a tremendous potential in these forests that could either lead to devastation through forest fire and catastrophic carbon release, or stewardship through utilization, planning, and management. While some Permaculturalists would like to see these trees felled on contour and left on the mountain, and others pre-consumed with the potential of the Loraxian “Once-ler” effect, the Forest Service is nonetheless gearing up for the largest standing dead timber sales they have ever done.  The BLM is continuing to address the last 100 years of forest mismanagement through its massive mitigation efforts as well.  Biomass is all around us and is happening. Incidentally, it is presently the largest source of renewable energy generation in the US, more than solar, wind, and hydroelectric combined!

The beetle-kill timber of Colorado can be used for locally produced, value-added lumber and forest products, which over the long term can maintain rural jobs and strengthen local economies. The by-products, namely wood chips and/or sawdust, can serve gasification facilities which are like molecular deconstructionalists. They render the basic constituents of organic material into their fuel compounds, hydrogen and carbon monoxide.   These facilities not only produce electricity round the clock 7 days a week, but also produce hot water for heating greenhouses, district heating systems for towns or campuses, or for residential and commercial users.  Gasifiers are not limited to just wood chips either, but the same facilities can turn our garbage (plastics, tires, and all other organic wastes) into BTUs as well. Landfills are a drag on municipal budgets and release methane into the atmosphere, which is 23 times more powerful than CO2 as a greenhouse gas. They might be a thing of the past in the not-so-distant future.

The other valuable co-product of gasification is the biochar of wood-chips.  Biochar is the origin of the old and extremely fertile soils of the Terra Preta of the Amazon.  Incorporated into agricultural or forest soils, biochar serves as a habitat for microorganisms, neither being consumed nor destroyed. It holds water and nutrients, provides decent crumb structure and tilth, and acts as a catalyst for optimal soil processes. Researchers from Cornell University have said biochar could “revolutionize” contemporary soil science management, as biochar additions to soil can boost yields up to 4 times.

Not only does biochar increase solar and carbon banking through enhanced growth, but for every pound of biochar produced and put into soils, there are 2.5 pounds of CO2 genuinely and permanently sequestered from the atmospheric carbon cycle.  In this light, woody biomass is a multi-faceted renewable energy approach. In fact, some perceive biochar to be a globally significant asset in sequestering carbon to fight rising CO2 levels and global warming.

High-nitrogen biomass  

Complementary to woody biomass that is characterized with a high carbon content and its energy released via thermal processes, high nitrogen biomass would be everyday compost material:  food waste, weeds, manure, and good ole sewage.  This material is decomposed biologically via anaerobic microbes from the kingdom Archeae.  These ancient critters were some of the first on Earth and are responsible for the Eocene solar gas deposits under your local National Wildlife Refuge!

Commonly known as biogas digesters, these vessels of microhusbandry convert organic material into not only methane-containing gas, but high-grade fertilizer as well—also an important resource for civilization. The European Union is well advanced in producing and refining this biogas into biomethane.  For them, it is a matter of regional biogas plants tied together into a pipeline network that feeds a central scrubbing plant, which then finally feeds the larger natural gas pipeline customers.  In Sweden, about as much biomethane is used in vehicles as natural gas.  A German study also showed that using biogas digesters to produce biomethane, per hectare, could get them 3 times as far as biodiesel, and 3.5 times as far as ethanol.

In America, there is not as much activity with the scrubbing and compressing of biogas into biomethane; however, the landfill of Columbus, Ohio just launched Phase 1 of a landfill-gas capturing project.  The project is cleaning and compressing the landfill gas (methane) into compressed natural gas (CNG) and has established a fueling station that is fueling cars and trucks, as well as generating electricity.  The facility will be distributing about 250,000 gallons of gasoline equivalent per year, and they expect the landfill to produce for over 30 years.  Closer to home, the Denver Metro Wastewater treatment plant generates 4 megawatts of electricity from their biogas digesters.

Pumped Hydroelectric Energy Storage (PHES)  

Colorado is well suited to utilize pumped hydroelectric energy storage with its mountain heights and presence of water.  It has a proven track record with 685 megawatts of storage potential in 5 different sites.  The basics of pumped hydroelectric are that during times of low demand (early morning hours), or when the sun or wind is blasting away in excess of demand, they can pump water up to a reservoir in the mountains. During times of peak demand, at night, or cloudy windless day, they can run that water down through a penstock like a normal hydroelectric generating plant: 75 percent efficient, graceful, and rapidly effective.

Compressed Air Energy Storage (CAES) 

With this storage method we can take the low-demand cheap energy, or wind or solar surplus energy, and run compressors to pack air in large caverns, like old mines, caves, or expired wells.  When needed, the compressed air is heated with a little natural gas and run through turbines to generate electricity.  New developments are under way that has the compressor up in the nacelle where the generator usually is located on a wind turbine.  As the wind turbine spins, it sends compressed air rather than electricity down the tower to the cavern.

Two plants currently exist with CAES, one in Alabama that has a power production capacity of 110 megawatts with a 26-hour reserve, and one in Germany that is 290 megawatts.  Both of these sites use solution-mined salt caverns that were created specifically for this purpose. Efficiencies are about 50 percent on CAES.

Electrolysis of water  

The simple principle of electrolysis of water into hydrogen and oxygen with electricity from intermittent wind or sun can be applied to storing these resources when they are available, and using the stored hydrogen to run back through fuel cells or combustion engines when needed.  This is simple, clean, and has efficiencies of 75 percent.  Hot water production is also another resource.  Projects are under way in Ramea, Newfoundland and Utsira, Norway.

This overview of energy storage technologies is not exhaustive, but a sampling of what can be done.  The most accessible methods are not so much technologies as good design, such as passive solar architecture, and using heat sinks for hydronic systems.

In this time of political, economic, and technological transformation, now is the time to design this new era.  While we do this, we need to look at its degree of integration, what byproducts it utilizes, and how many diverse value streams it produces.  A model of distributed generation from diverse sources tied in with applicable storage approaches can be a resilient solution to an outdated transmission grid, rising electrical demand, and new rural generation plans. As much as we have to consider economies of scale, a local, decentralized approach that values abundant and diverse jobs, custom engineering, and quality of life will thrive on investing in its own infrastructure. The centralized approach, on the other hand, has traditionally exported revenues and imported job-replacing economies of scale.  Which is better is up for debate.  What is certain, though, is that opportunities that stimulate both nutrient and fuel cycles, such as biomass resources, are a good cogenerative match to communities that value not just one asset of the Earth, but several.  “Land, then, is not merely soil,” said conservationist Aldo Leopold in 1949; “it is a fountain of energy flowing through a circuit of soils, plants, and animals.”

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