Geoengineering: Green Hubris? Good Sense?

Earlier this week the Wall Street Journal ran an article by Jamais Cascio entitled “Its Time to Cool the Planet”, the crux of which is the author’s sentiment that worsening effects of global warming, combined with an abysmal public policy response, have trumped his previous reluctance to endorse our taking the planet by the helm and driving it.

The answer to this perfect storm of impending calamities is a shock dose of geoengineering- “a more deliberate manipulation of the environment, rather than a byproduct of other activities”- coupled to a steady diet of low-carbon activities.  In other words, we can’t afford to play nice any longer.  It’s time to bring out our secret weapon… our ace in the hole: geoengineering.

I would love to say something intelligent about the subject, but instead will offer an anticlimactic riposte of archetypal proportions: Mr. Cascio’s premise is beyond my capacity to evaluate.  It is troubling, I know.  How can one who has sat through the requisite derivation of the Navier-Stokes equation at an ABET Accredited institution- one who once wielded the Biot-Savart law with ease- be unsure on this rather non-trivial point?  Do we launch a few million tons of sulfur dioxide per year into the stratosphere or not?

(Thankfully those of us familiar with the motion picture franchise Speed have mentally prepared ourselves for making heroically correct snap decisions in moments just such as these.)

Let me offer an alternate framing of the same sentiment: how many Journal subscribers actually are in position to assess the validity of this position?  My opinion is none.

And yet… this premise has elicited, and will continue to elicit, all manner of condescending rebuttals, knee-jerk responses, triumphant declarations of solidarity and support, at least one bumper sticker campaign, and the odd affirmation that the path forward to planetary salvation has finally been made clear.  We are an excitable tribe, if nothing else.  And this, I suppose, was the point of the exercise.

Let’s move on.  I think this notion of geoengineering and the surrounding strongly worded language regarding the future of the planetary environment and our ability to survive it, or lack thereof, points to a much more interesting, underlying and pervasive dilemma.  We are faced each day in this world, both individually and collectively, with seemingly intractable challenges for which the solutions are far from clear.

If we’re honest with ourselves, more often than not we don’t have the answers.  This is difficult for us.  It is stressful, threatening, unrelenting, and overwhelming.  So, we convince ourselves we do have the answers…  (Convince here means anything from pure, gut-feel side-taking, to mathematically proving with limited assumptions, to logically arguing based on limited evidence, to following the advice of other people whose job involves knowing the Right Answer.  Limited here means anything less than the whole.)  More importantly we convince ourselves of different answers, and then are obliged to defend those differences, (sometimes to the death).  As soon as the choice is made to embrace a position as a means of alleviating the pressure of not knowing, there are only two choices: defend the position by attacking other positions, or wade back into the much deeper water of the question.

I view this challenge that lives in each of us as fundamental to the global challenge of achieving sustainability.  We don’t know and can’t predict precisely what will happen in the next century.  We don’t know and can’t predict what the outcomes will be if we put mirrors in space, sprinkle iron filings in the ocean, launch sulfur dioxide into the stratosphere, or seed clouds with Herculean sea water pumps.  We don’t know and can’t predict whether or not we’ll look foolish tomorrow for the decisions we make today.

Besides our capacity to identify and mathematically describe relationships between observed phenomena, we also have the very human ability to take a look back into that gaping unknown, even to sit there for a time.  Doing so may not build rockets, but it could build wisdom, and I think we will need just as much of that as we need of supercomputers and climate models.  Probably more.

Geoengineering could be age-old hubris in another guise.  Or maybe it is the right move and the right time.  Who can say?  We will collectively and individually learn many things along whatever trajectory we take, and if what we learn includes some wisdom about how to use what we do not know as a vehicle to bring us together rather than drive us apart, it will be a step closer to sustaining something worth keeping.

by Michael Mark, PE

Energy Literacy – Does it Matter?

A lead story in the June, 2009 Green Building News ezine begins with the following headline:

“…Community College Achieves 70 Percent Energy Reduction”

This has the desired effect of making one set down the coffee mug, consciously reduce both spinal curvature and pupil dilation, and snap that left mouse button with a little enthusiasm.  The article then goes on to note that the Ohlone College Newark Center for Health Sciences and Technology consumed roughly 69% less electricity and 72% less natural gas than a “similar facility designed to meet California’s Title 24 requirements.”

Well, that’s not quite the same thing. (But still handily quite impressive.)

Then… according to the article the project features 35,000 square feet of photovoltaic panels capable of generating “710 megawatts of power”.

Here we need a time-out and a chance to consult with the Committee on Reality for a ruling on What Could Really Be Happening.

If the 35,000 square feet is correct, that probably equates to 1,850 – 2,250 kWh per day, or an average power output of 150 kW or so.  Now if we take that 2,000 kWh per day and apply it to 365 days of the year we could produce an annual electrical energy total of 730,000 +/- kilowatt-hours.  That is equal to 730 megawatt-hours, which is close enough to “710 megawatts” to suggest we now understand What Could Really Be Happening.  The site probably has the capacity to generate close to 710 MWh over the course of a year.

There is one final nuance here.  Given the fact that the LEED methodology for calculating energy consumption in comparison to a similar (but fictitious) baseline building allows on-site PV power to be netted out of total building electrical consumption (for calculation purposes), it is plausible that the building may have used 69% less electricity from the grid, but not 69% less electricity overall.  The on-site generated power would still have been used by the building, but the LEED methodology properly gives credit to on-site renewable power generation in the rating system by allowing the design team to deduct such power “off the top” of its building energy model.  The design building energy model is simply not charged those energy costs in order to credit the improvement over a building without the on-site renewable generation.  Its a LEED point calculation thing.

The Ohlone College web-site suggests the solar system actually covers 38,000 square feet, has a design power output of 600 kW, and will meet roughly 45% of the campus’ annual electrical energy needs.  If the 69% reduction that was reported included this PV generation, as would typically be the case in the LEED calculation process noted above, then this suggests that the building purchases about 1/3 the grid electricity of a comparable building, and uses about 2/3 of the electrical power of a comparable building.  These differences are noted in the graphs below.

The first depicts what one may be led to believe from the article headline:

This second depicts what is likely happening in point of fact:

A quick web search turned up two other articles on the building, one which suggested the building utilizes “energy cogeneration from 1,585 square feet of rooftop solar panels”, and an article posted at AOL that states the building achieved a “69-percent reduction in purchased electricity”.  The AOL article seems the most accurate, and I like that the AOL article went to the environmental and financial bottom lines by giving the calculated carbon reduction and annual savings- although it is noteworthy that an ROI assessment of the energy systems is absent from this column that appears in the AOL Money & Financial section.

Total building energy savings were estimated at $130,000/yr, but what did the system cost?  I believe a reasonable estimate is that the photovoltaic system cost in the neighborhood of $2 million ($5 per watt-peak).  If this cost were amortized over twenty years at a 4% interest rate the annual payment works out to roughly $147,000.  Assuming all of the $130k energy savings may be attributed to the system, which I think is a stretch given the enthalpy wheels and ground-source geothermal HVAC systems the building also has, this equates to a 13% premium in energy costs for the first year, with prices locked in on nearly half of the facility’s energy portfolio for the next twenty years.  Not a bad deal, given that a significant portion of the school’s future energy pricing is “locked-in”, and insulated from market fluctuations in electricity, carbon and fuel costs.

If we assume, on the other hand, that electricity costs the school an average $0.14/kWh today, then the 710,000 kWh generated per year by the PV system saves about $100,000/yr.  Compared to the projected cost, this would be a losing investment, unless the school received financial assistance in the form of grants or rebates (both of which are likely available in some form), or my estimate of capital cost is considerably incorrect.  Both could be.  And both would be meaningful factors to highlight in a review of this project.

Why does any of this even matter?

Unless one is an engineer, architect, building professional, or simply an astute reader of energy-related documents, one may never have been educated or trained about the basics of energy production and consumption, despite the fact that we’re all involved in these transactions every day.  Such an individual’s context for discussions of energy and what can reasonably be accomplished will come from popular articles like these, which occasionally miss the mark and seldom give the “whole story”.  If the point is merely to highlight a great building project, mission accomplished.

At some level the reporting noted above is sloppy, however, particularly given the alleged target readership: green building and sustainability professionals.  Assuming a link between an increasingly energy literate design community, policy-making sector, and general public, and the quality of our individual and collective decisions, I think it is clear we can and should work to ratchet up our energy literacy.  Why should we or should we not put public funds into subsidizing various energy technologies?  Where do our green energy investments achieve the greatest carbon reduction and financial returns?  What is the network of factors that makes investments like the one discussed here worthwhile?  Why and how is this success repeatable?

If it seems a harsh verdict, I would buttress the verdict with the sentiment that to be fair the same elevated standards should apply indiscriminately to all such articles, whether about nuclear power plants, building envelopes, coal-fired power plants, wind turbines, cogeneration systems, or fluorescent light bulbs.

Only in this way will we collectively learn, and develop increased literacy regarding the nature of the challenges we face and the solutions that are available.  And I’m of the opinion that it matters.

A Chilling Enigma

(Note: Be forewarned this post reaches a stunning conclusion.)

Perceived through the constellation of undisciplined data processing algorithms deployed by the untrained Mind, it would appear that chilling and heating are but two sides of the energy coin- the yin and yang of thermal comfort. Do not be deceived, however. One is of a very Direct Nature, the other of a quite Indirect Nature, the relevance of which is to follow.

Consider a few rhetoricals…

What is the chilling equivalent of fire?

(The reader is encouraged to disregard the highly misleading content of certain beer commercials when reflecting upon this question.)

How many towns have a Volunteer Chilling Department to protect their inhabitants and property from the unexpected outbreak of bitterly cold, self-propagating, potentially out of control and in such cases terribly destructive phenomena?

One challenge in evaluating energy processes is understanding that although we can mathematically convert and express all forms of energy in the same units (e.g. kilowatt-hours or kWh, British Thermal Units or Btu’s, or, much to the chagrin of first-year engineering students throughout the English-speaking world, the quantity of slugs accelerated through a distance), they are in practical terms not all quite the same.

It is one thing to say a kWh of electricity is equivalent in energy content to an 807.3 lb sack of bricks located 0.621 miles above the ground, and another to figure out how to manipulate that sack of bricks properly so that by the time it hits the ground you’ve toasted 40 pieces of high grade spelt bread. And by toasted I mean charred.

Chilling, like the generation of electricity, requires a somewhat more convoluted energy conversion path than heating. The most straightforward means of generating chilled water are a) vapor compression refrigeration cycles, b) thermal absorption refrigeration cycles, c) evaporative cooling, and, when the outside air is cold enough, d) free cooling or direct sensible heat exchange with the outdoors. For the moment, we’ll focus on a) and b), because the last two options are impractical in hot, humid areas where the need for chilling is most intense, and because they also consume far less energy (and thus have less environmental impact)…

This first astoundingly blue chart shows the unit of chilling effect produced per unit of energy input. The electric drive chiller and heat pump are vapor compression cycle units, and the others are thermal absorption cycle units. No distinction is made between the type or quality of energy going into the systems.

This is not the whole story, however. It would seem that the vapor compression units are a much more strategic use of our energy input, but in order to run them we need high grade energy in the form of electricity (or rotary shaft power, also a high grade form of energy in the grand scheme of things). If an assumed 30% energy efficiency is included in the calculation to account for lost heat at central electric generating stations and grid transmission losses (based on the national average), the chart then changes a bit. See below, and note the Doppler shifted color scheme which subconsciously connotes an eroding confidence in our previous lucubrations.

The typical electric drive vapor compression cycle chiller still looks the best, but the gap has narrowed. Now, remember the other 60% of the energy input to electrical generation processes that is lost as “waste heat” because it is remote from the people and places that could use it? Let’s consider using that as our energy source. That could be used to run one of the absorption cycle chillers if it were a resource available on-site. There are also various and less-frequently-deployed heat engines such as packaged Organic Rankine Cycle units (vapor compression chillers with a different refrigerant, run backwards) that could be used to convert a fraction of that energy to electricity, and in turn run an electric drive chiller. Comparing these two scenarios we obtain the following (a stunning purple color scheme reflects compliments a stunning result):

The lower efficiency of the electric drive chiller reflects the diminishing efficiency in converting thermal energy into electrical energy as the temperature of the thermal source decreases. The Organic Rankine Cycle units just can’t convert low grade heat into electricity nearly as efficiently as a coal-fired power plant can convert high grade heat into electricity. The Btu’s are there, but we can’t convince nearly as many of them to become electricity once they’ve slid this far down the thermal value chain (which is temperature). Keep in mind that the low grade heat is generated as a byproduct for most forms of electric power generation serving the Grid. In other words, this tree is falling in the forest, whether you’re there to hear it or not. Just because you don’t have on-site electric generation pumping out waste heat faster than you can use it doesn’t mean its not happening somewhere else as a sidebar to the electricity you are consuming.

Now, in this last graph we’ll compare the energy input, carbon footprint, operating cost, and capital cost- ballpark figures only using Washington, D.C. energy costs for fuel and electricity- of two scenarios: a) using grid electricity to power an electric drive chiller (to make all options equal, we’ll make enough electricity to power the chiller plus an additional amount equal to the on-site generation), and b) using waste heat from on-site cogeneration to run a single-stage absorption chiller (assuming 80% of the waste heat is used and all of the electricity).

(Who needs color graphics, anyway?)

And now for the moral of the story: on-site cogeneration has the potential to provide chilling with low grade heat, while reducing your carbon footprint, energy cost, and your total energy input footprint. Although it is much less efficient than an electric driven vapor compression cycle chiller, it is able to utilize low grade heat as its energy source, and over 2/3 of the national energy input into electric generation processes is lost as heat to the atmosphere (or a large body of water).

And now for the real moral of the story: there are, according to the 2003 Energy Information Association Commercial Buildings Energy Consumption Survey, 71,568 million square feet of commercial buildings in the US. If each 200 square feet requires one ton (or 12,000 Btu/hr) of chilling effect on a hot day, the US needs about 400 million tons of chilling. Given the whole country doesn’t peak at the same time, this is without a doubt and unequivocably a high estimate (for space cooling).

Having said that, if we harness the waste heat from the electrical generation processes that go towards satisfying the very approximately 150 GW (yes, those are giga-watts) in electrical power those buildings consume, and use it for chilling, we could cover 15% – 20% (nearly 30% with double-effect absorption units) of the instantaneous chilling demand of the Commercial Fleet. We could cover more with thermal storage.

Lastly, if we actually were crazy enough to do this, (its not exactly practical on such a scale, I admit, but the trend is interesting), we’d also reduce the peak electrical demand at commercial buildings on hot days by roughly 30 – 40 GW, or nearly 25%. To put that in perspective, one coal fired plant generates about 1 -2 GW of electrical power output.

by Michael Mark, PE

Too Much of a Good Thing?

An article in the May/June edition of GreenSource Magazine about the recently completed Melbourne Council House 2 highlights a key lesson for all of us: the purchase and installation of as many “green” widgets as the budget and site plan can accommodate does not a successful project make.  This building would appear to have more whiz-bang features than the latest handheld, not the least of them being the prominently placed building integrated wind turbines (prominently featured in 5 of the 8 photo’s of the project) that “were over-engineered due to safety concerns and are too heavy to spin under common wind conditions.”

Hey- whose side am I on, anyway???

I’ll answer that: I’m on the side of everyone that wants to see the very best results possible produced whenever and wherever the opportunities present themselves- not by generating the greatest show necessarily, but by making sound decisions.

I confess I found the article disheartening because here’s a building project that admittedly spent 20% of its budget on green technologies, AU$11 million, and ended up (according to the Architect, Mick Pearce) with multiple poorly utilized systems.  “Poorly utilized” were not his own words, but in my opinion are implied by the article.  Let us have an out-of-context quotation from author Russell Fortmeyer:

“Building-scale black-water plants remain a relatively experimental technology in Australia, since many city councils can be skeptical of water quality, not to mention the systems’ high energy use and capital cost. Pearce, for one, thinks the technology only makes sense when it’s sized to feed several buildings, a precaution they took in design, but haven’t used in practice, for CH2. A 60kW cogeneration plant—which generates electricity and usable heat, and also powers an absorption chiller—on the building’s roof is another piece of technology that Pearce wouldn’t use again, unless multiple buildings could benefit. ‘You end up with too much waste heat that you can’t use,’ he says of the relatively small CH2.”

(The sound of a vinyl record rapidly screeching to a halt.  The protagonist freezes, spins silently to his right, ducks out of the all-natural moonlight and smears his back into an airtight fit against a low-VOC stained bamboo composite wall.  He waits a moment.  Catches his breath.  Pulls out a laminated set of 4”x6” construction plans from his breast pocket and flicks on a fuel-cell powered LED headlamp.)

The comment about the cogeneration system bears some discussion.  First, consider what the article has to offer regarding the building heating and cooling systems:

One, The Design Basis: Temperatures in Melbourne range between 50 and 80 degrees Fahrenheit throughout the year, with few exceptions.  From the start this is not a building with extreme climate control challenges.

Two, Thermal Storage:  Salt solution PCMs (Phase Change Materials) were employed to provide cool storage.  Frozen at night, they melt during the day to produce chilled water.  According to the article, “…by sizing the PCMs for nighttime use, we could afford the system.”  I haven’t done the research recently, but last time I checked these were indeed fairly expensive toys.

Three, More Thermal Storage:  At night, cool air is blown through the building, which cools thermally massive concrete floors.  This results, according to the article, in a window of several hours each day when conventional chilling is not required, equivalent to a reduction in chilling demand of approximately 20%.  This strategy makes some sense.

Four, Chilled Water Production:  Sources of chilled water appear to include, first, an absorption chiller that is part of the cogeneration system.  Absorption chillers use low grade heat to produce chilled water using some chemical sleight of hand in lieu of a refrigerant compressor.  Second, the PCM’s.  And third, there appear to be electric-driven chillers in the building, as the article states that with PCM’s, “…the building reduces its dependence on conventional chillers.”  This latest is not clear, as it could be the case that the bulk of the chilling comes from stored night cooling through the PCM’s, with the balance from the cogen plant.

(Our protagonist completes his reconnaissance.  He unpeels himself from the building façade, secures the headlamp, and makes a satellite call to an automated system that will preheat his oven and cue up his Tivo- a micro-electronic-electromagnetic energy storage system.  The Stanley Cup is on, and he’s five minutes past the face-off…  He spins on his left heel, strides into the building, takes the elevator to the fifth floor, enters his apartment, and turns on the game.  One can never have too many toys…)

If the cogen system generates 60 kW of electricity, the absorption chiller consumes at most 120 kW of waste heat, or enough to generate about 25-30 tons of chilling with a single-stage absorber.  The heat could also be used to make roughly 700 gal/hr of hot water for domestic uses or building heating as required.

The building is approximately 134,000 square feet, and maybe on an average summer day has a median chilling demand equivalent to 175-250 tons?  Maybe more?  Maybe less?  The point is that the cogeneration plant’s waste heat should easily be utilized by the building systems…

It stands to reason that there should almost always be a home for the waste heat from this 60 kW generator.  During times when there is not, the connotations of the article suggest that it is most likely because a) the PCM’s stored plenty of cooling effect overnight, were saturated, and the building did not need another source of chilling, b) domestic hot water had no need for topping off, and/or c) the PCM system is not piped to accommodate the influx of chilling effect from the cogeneration system.

In either case, it does not appear an optimal integration of technologies was achieved.  Using PCM’s to drive cogenerated chilled water off-line, if indeed such occurred, represents an example of wasted capital and energy.  For a fraction of the capital cost invested in green technologies, a pipe or two and a circulating pump could take all the excess chilled water from an even larger cogen plant over to the adjacent building, which most oddsmakers will agree is not equipped with PCM’s. The wind turbines represent another excess and under-utilized investment.  The real challenge of new technologies is achieving the proper integration and balance between the technical pathways they afford.

The article makes the point several times to suggest some of the technologies would have made a better fit on a multi-building scale.  The article also notes this building was built in the parking lot adjacent to another government building.  Where better to make the demonstration at the appropriate scale?

In my opinion, this article inadvertently sums up how far we really have to go.  Those on the fence will view this as a landmark example of precisely what is flawed with a “Sustainability Movement” too little grounded in reality.  I couldn’t disagree.  Many of the features, like the use of ambient cooling at night with building thermal mass, are ingenious- but I don’t see the need to couple them to other expensive or under-utilized assets (gadgets).

Despite investing the reported AU$11 million in capital, systems in some cases don’t run or appear to compete with one another. In terms of sustainability the same investment in energy and/or water saving projects throughout that city block, viewed as a single system, could likely have produced far greater returns (both environmentally and financially).

Perhaps the real challenge of sustainability is thinking beyond the nearest box?

For a more in-depth review of the building systems, visit the Melbourne city site.

By Michael Mark, PE

The Carbon Content of Cooperation

If you imagine trying to tile a bathroom with the topography of Idaho and a perimeter contour with the juts and jags of a Manhattan skyline, using a bag of little tiles that undergo a quantum change in shape every ten degrees of temperature change, you a) need to rethink your remodeling budget, and b) have outdone yourself in terms of visualizing the challenge of precisely matching electrical and thermal outputs from discretely sized pieces of equipment to an agglomeration of energy loads with time-varying electrical and thermal energy demand profiles (a.k.a. The Grid).

Not only do the electrical and thermal needs of every given building change with time of day and season of the year, so do the respective quantities of energy available from a fixed piece of generation equipment- some moreso than others, and none perhaps moreso than those in the renewable family.

The Grid embraces the complexity of these details through the deployment of a strategy well-known to quantum physicists everywhere: coarse graining.  Just as an apple is a seething, manifestly incomprehensible mapping of countless wavelets of energy onto time and space, (but really just an apple), so The Grid looks like an enormous and singular Chunk of electrical energy supply, (but really is  a LOT of coherently entangled toaster ovens).

I see one tremendous upside to the grid being its ability to function as a “sink”, in the classical, Newtonian, Thermo One sense of the word.  Right now, the Grid receives energy from a relatively small quantity of high-voltage generators, and distributes it to a relatively large quantity of low voltage consumers- namely the World’s Largest Ever Fleet of Thermostatically Regulated Toaster Ovens.  The same infrastructure could also be used to agglomerate and locally equilibrate the time-varying and never perfectly matched electrical and thermal outputs of an expanded Fleet of Cogenerating-District Energy Linked-Renewable Sunshine Supplemented Toaster Oven Repositories (a.k.a. Real Estates).

It does require a certain degree of level-headedness, however.

If you have read any of the previous posts, you see we have a tendency to advocate for combining thermal and electrical generation in much smaller bits, at a location near you, thereby significantly increasing fuel energy utilization efficiency and reducing greenhouse gas emissions.  We have suggested previously that applying this strategy to just one half of one-third of the current Fleet, we could cost-effectively reduce the amount of fuel we consume as a nation for electrical generation by about 10% (and GHG’s commensurately).

The Title of this post refers to the fact that some collectively endorsed consensus-based decisions, sometimes referred to as “policies”, “political footballs”, “cooperation”, or “travesties” depending on your perspective, could streamline this process and allow us to access said greenhouse gas reductions.  Such decisions may ostensibly include, but not be limited to, the following:

1)    So-called smart-metering combined with a system of exchange that allows Owners (specifically those located in energy dense urban locations) of multi-functional generation equipment and/or of Sun and Wind Hoarding Devices, to receive time-varying compensation for electrical energy supplied to the Grid at prices more closely related to the “real” cost of energy at that 15-minute window of time.

2)    Policies that allow for sharing of excess electrical energy at mutually agreed upon prices with One’s Immediate Neighbors, without engaging most of the nation’s Legal Talent to debate the Constitutional Suitability of such a heinous act.

3)    A carefully considered and partially contrived Instrument for the application of our funds to the Problem of Needing (and needing to pay for) Some Certain Amount of Reserve Energy Generation Assets So Everyone Has Lights in the Event Some of the Other Assets Don’t Work.

Such unprecedented cooperation would utilize the existing grid more like a sink than just a source, and enable a more flexible and competitive marketplace for local energy generation.  Or to rephrase: a Lotta’ Carbon for a Little Cooperation.

By Michael Mark, PE

Big Energy Numbers

The Energy Information Association is the federal repository for national energy trivia- not exactly a trivial mission these days.  The statistical arm of the DOE, these guys spend their days tracking everything from uranium reserves to commercial building energy consumption.  They publish a report each year called the Annual Energy Review, which takes a look back at how much energy our great nation consumed, including a detailed analysis of where it came from and where it went.

One interesting chart, included below in a quasi-legible format, shows the amounts and types of raw energy feedstocks that were consumed in the production of electricity.  The numbers given represent quadrillions of Btu’s (British Thermal Units).  One Btu can heat one pound of water one degree Fahrenheit, and it takes roughly 1,000 Btu’s to boil a pound of water, all of which means we invested sufficient terrestrial fuel energy reserves on electricity in 2007 to boil roughly 5.1 trillion gallons of water, (or roughly the amount of water discharged by the Mississippi River into the Gulf of Mexico over a 2-3 day period).

Back to the chart: coal, for instance, provided 20.99 “quads” of energy to processes that were used to convert the stored chemical energy in the coal into electricity.

This pastel-colored complex of graphical information suggests some interesting points.

First, of the 42.1 quads of fuel energy input into electrical generating processes (the sum of energy inputs at left), 14.94 were returned as electricity.  Nearly 28 quads are described as “Conversion Losses”.  This results in a total national average conversion efficiency of about 35%.

Second, of the 14.94 quads of energy in electric form, about 14% or 2.09 quads, are spent to support the overall effort.  1.34 quads are expended on the grid to “push” the energy to the end user (yes, the grid more or less pushes back to a certain extent), and 0.75 quads are spent back in the power generation facilities to run supporting equipment.  So, in the final accounting, 30.5% of the energy spent on electricity generation processes results in useful energy at the customer’s site.

This means that a unit of electricity generated on-site in a combined heat and power system, assuming a large percentage of the waste heat is recovered and beneficially utilized, avoids approximately 2-3 units of raw fuel energy input (on average).  On-site generation can typically achieve greater than 30% electrical efficiency, and allows for recovery of waste heat to support heating and cooling.

If 50% of the commercial sector employed such a strategy (or had its combined electric and thermal needs met from district energy plants), and if 50% of the waste heat available from on-site generation were beneficially utilized, US fuel-energy consumption for electric power would drop by approximately 10%, or roughly 4.4 quads.  Water consumption for power generation would also drop by roughly 40-60 billion gallons per year. I see such buildings as being the stationary equivalent of hybrid vehicles: they assemble readily available components into more efficient systems.

Capturing 50% of the commercial segment with more efficient means of generation seems like a large number, as it would mean retrofit of a vast number of buildings with new technology, the integration of which may even require retrofit of existing heating and cooling systems to enable beneficial use of recovered heat from electric generators.  Its frankly a ridiculous number, but so are all of the numbers in play here.

At an assumed installed cost of $3,000/kW, however, a value that is high for today’s marketplace, a very muddy order of magnitude number for installing this type of generation is about $300 billion.  To put this into perspective, in 2008, some estimates suggest that $120 billion went into renewable energy systems in the US alone, and others suggest that as much as $1.5 trillion will be invested into new electric generation capacity in this country over the next 15 years as older plants retire and demand for energy continues to grow.

By Michael Mark, PE

Green Power: Buy It or Make It?

As noted previously, most commercial buildings utilize more electric and thermal energy than can be cost-effectively harvested, processed and stored from on-site renewable sources using present-day systems. Exceptions to this rule include abandoned airplane hangers, Mesoamerican pyramids, lunar bases, and strategically located terrestrial structures built and operated exclusively to prove a point.

There are then basically two options: purchase the additional energy required or generate it on-site. Typically thermal energy needs like chilled water, steam, or hot water are generated on-site from purchased fuel, and electrical energy needs are met by purchasing power from the grid. It is possible to purchase green or renewable power from the grid, although at the moment this action appears to fail Kant’s categorical imperative test: if everyone did it we’d be faced with a political, financial and physical impasse of non-trivial magnitude.

(Our grid at present requires a certain balance of energy generation types to function as it does. To generate all of our power from renewables tomorrow would require investments in infrastructure that would dilate the pupils of the even the most staunchest of Stimulus Advocates.)

Tabling for a moment the implications of an unlikely explosion in the demand for premium cost green power purchases, the present cost of renewable power is roughly 10% greater than “normal electricity”. And contrary to what is possibly a common belief, you probably don’t even get the green electrons you bought. The grid is a topic for another day, but suffice it to say that electrons are like a pack of over-caffeinated morning commuters in a [insert the name of your favorite densely populated metro area here] crosswalk: they follow the path of least resistance. When you buy green power you ensure it makes its way onto the grid somewhere, but if it is not generated in your specific area this may not reduce the need for grid improvements or additional power generation facilities in your neighborhood.

As such, renewable purchases are subject to the same grid losses and thermal inefficiencies as “conventional power”.

On-site electrical generation has the ability to reduce grid inefficiencies associated with a site’s energy use, to reduce a site’s overall emission contribution, and to reduce the cost of meeting the thermal energy needs through cogeneration. An assumption-laden chart will help to bear these points out. (Fine print to follow impression-making graphics.)

The emissions comparison for NOx and CO2 assume that the “Conventional Building” is heating with natural gas and utilizing grid average power.  The cogeneration option is also based on natural gas.  To estimate the atmospheric emissions for grid-purchased power in your area, visit this EPA site.  If the base scenario were based on electric heat or a fuel of a more questionable post-combustion character, the spread would be greater.

The “Energy Expense” comparison assumes electricity costs $0.14/kWh and natural gas fuel costs $8.50/MMBtu. Maybe realistic, maybe not. Like a good building design, a good on-site generation system must be site specific and integrated with process needs.  This is a comparison of operating costs only, and does not factor in the cost of capital or any other real world factors sure to make an actual project analysis cover a rich and varied emotional terrain.

By Michael Mark, PE

Cogeneration Goes Mobile

Cogeneration, the thermodynamic answer to biodiversity, is the simultaneous transformation of input fuel energy into multiple energy product outputs- such as electricity and steam, or electricity and chilled water.  Cogeneration typically results in a higher fuel energy utilization than a plant producing only one product, or it results in a comparable utilization efficiency while producing higher value products such as electricity or chilled water.

A boiler can be quite efficient, but its cogeneration prowess is limited to the simultaneous production of heat and some steady low frequency rumbling noises.  A boiler plant with a backpressure steam turbine, on the other hand, will generate heat to keep a fleet of buildings warm like it always did, plus some electricity on the side, and a much more interesting acoustic spectrum.  In this case the fuel utilization efficiency may not improve, but the quality and value of the energy products generated will.

The ability to cogenerate energy products is a distinct advantage of distributed generation and district energy systems, because they are able to maximize their fuel utilization and minimize the fraction of energy spent as “waste heat” or grid transmission losses (of electricity).  Refer to Small is Profitable Benefit 160.

(The profoundly anticlimatic photo opportunities and gallimaufry of vendor hats, jackets, and stenciled mouse pads that result from these projects are two additional and often overlooked benefits.)

Automobiles have never really gotten into this game- (transporting boilers and steam turbines is not a task to be taken lightly)- but that could be changing.  In “Harvesting Waste Heat to Save the Climate“, Institute for Science in Society has noted that German automeisters BMW, as well as General Motors, are researching the generation of electricity from engine exhaust heat.  They are both proposing improved thermoelectric generators: systems that utilize the thermoelectric effect to generate electric current when the junctions in a loop of two dissimilar metals are maintained at different temperatures.

The technology is an interesting fit for the transportation application because it is presumably bereft of moving parts.  So, although other technologies offer potentially greater waste heat utilization efficiencies, they are not likely to be as light or as simple, two key factors in this application.

BMW has suggested the technology could yield a fuel efficiency improvement as high as 5%.  If you drive 15,000 miles in a year, and average 25 miles per gallon, and you don’t allow your driving habits to be psychologically affected by the exhilirating knowledge that your exhaust pipe is equipped with space age technology, this is a savings of 30 gallons per year.

By Michael Mark, PE

Energy Right-Sizing

Somewhere right around the 39th parallel on the east coast you will find a site that receives, on some reasonably conservative average, about 3 kWh per square meter per day of raw solar energy.  If you put a building there, and you find a way to harness and utilize all of that energy, (in which case you are very clever, indeed), you could on an annual basis heat, cool, and electrify maybe as many as seven stories of finished space (assuming current construction methods and building technologies).  That is the good news.

The barriers to such wanton success include: the time value of energy, the laws of physics and our current ability to apply them economically, public policy, and the taller building in the lot just to the south of you that hogs all the renewable resources.

Time value of energy means that there is too much solar cash flow in the summer, not enough in the winter, and no bank to store it in so you can even it all out.  Keeping energy around for just when you need it is expensive and difficult.  Life does this brazenly well, (polar bears are quite happy to eat nothing at all for months at a stint), but we haven’t quite figured out how to copy it yet.  Life performs amazing chemico-physical feats on a whim, while creating and wasting very little energy as heat in the process.  We, on the other hand, struggle daily with these concepts and do not enjoy such heat-avoiding chicanery as placing sunlight bit-by-bit into the shape of a tree: we are most comfortable working with things that burn as they transform.

It is certainly visually appealing.

Speaking in terms of universal speed constants, there is no heat engine known to humans that could convert sunlight into forms of energy we would like at 100% efficiency.  Plants, which are most definitely NOT heat engines, are about 2% – 4% efficient at converting sunlight to stored chemical energy (as biomass).  Photovoltaic panels do 3-4 times better.  And solar thermal systems can even beat 80% capture rates, but there’s only so much heat we can stuff into a building before we decide there has to be a better way.  Converting the captured heat into a more valuable form of energy, such as electricity, is fairly ineffecient.  And storing it for six months to use in the winter with current technology is work for Sisyphus.

So, realistically, the unabashed deployment of present solar/renewable technologies on, in, near, and cleverly juxtaposed with all the surfaces of a modern building can probably sustain the realtime energy needs of 1-2 floors of finished space.  Anything larger than that will almost definitely require energy imports.  That is sounding like bad news.

Our job until such time as energy is truly cheap and abundant is to use it and transform it as wisely as possible.  It is just about this spot where we aspire to enter the conversation.

By Michael Mark, PE