Author: William Driscoll

Distributed solar grid access fee axed in Arizona

By William Driscoll

Arizona regulators have repealed a grid access charge that applied only to customers with distributed solar.

“Under state and federal law, a utility may not discriminate” against customers with distributed solar, said a regulatory amendment that passed by a 3-2 vote.

Different treatment of solar customers must be justified “based on accurate data and consistently applied cost-allocation principles,” said the amendment, adding that the record in the rate case “contains no such evidence.”

The Solar Energy Industries Association, which filed over 300 pages of testimony in the rate case, “was able to prove that solar customers in Arizona pay their fair share of grid costs and do not introduce additional costs to other customers,” said Sara Birmingham with SEIA. The grid access charge had been approved by state regulators nearly a decade ago, she said.

Solar customers of Arizona Public Service contribute more to the utility’s cost recovery than non-solar residential customers served under two of the utility’s rate classes, tweeted Ben Inskeep with EQ Research.

The grid access fee was “making it harder for Arizona families and businesses to choose solar,” said Yara Marin with Vote Solar, which had filed over 200 pages of testimony.

The Arizona Corporation Commission amendment noted that “the recent Commission elimination of net metering for solar customers was in part intended to address a perceived cost shift from solar to non-solar customers.” The amendment added that “in that light,” the grid access charge “amounts to a penalty for customers who provide substantial public benefit in the form of private investments in local, pollution-free energy.”

Utility fees on solar have also been reversed in Kansas, Nevada and Massachusetts, said Inskeep.

Electricity storage in hot stones validated by $3.4 million investment

By William L. Driscoll

A long-duration thermal battery technology described to the California Energy Commission last December has gained credence from a Danish government investment.

The Danish Energy Agency will invest $3.4 million in a 10 MWh plant in Denmark to demonstrate the technology, which stores electricity as heat in small basalt stones. The system’s round-trip efficiency is projected to be 60%.

A U.S. project team aims to build a second demonstration project, twenty times larger, in the U.S.

Danish firm Stiesdal and its U.S.-based partner Magellan Stortech described the long-duration “GridScale” thermal battery system last December in a public workshop hosted by the California Energy Commission (CEC).

A thermal battery plant coupled with a solar farm could be configured to charge daily for 8 hours and discharge for 16 hours, the firms said. Or, because the hot stones would be stored in insulated tanks, the system could store energy for up to 10 days.

The two firms said they “look forward” to working with teams at the University of California Merced and the consulting firm E3 to “clarify the benefits that long-duration storage can provide,” as a follow-on to the CEC’s initial workshop on long duration storage scenarios.

The thermal battery system, already tested at 1:10 scale in Denmark, uses the principle of an electric heat pump to shift heat from cold pea-sized stones in one tank to hot stones in another tank, heating them up to 600 degrees C. The heat is later extracted at a constant temperature to drive one or more gas turbines to generate electricity. A modular design facilitates scaling, up to 1 GW capacity or larger.

As of December, Stiesdal and Magellan Stortech were exploring options for deploying a second and larger demonstration plant in the U.S., sized at 20 MW of 10-hour storage, or 200 MWh. The firms aimed for subsequent commercial-scale U.S. projects.

Advantages of the thermal battery system include the low cost of crushed stone, and the use of charging and discharging technologies that have been “applied for a century within other industries” and are well-suited for mass production, said Peder Riis Nickelsen, CEO of Stiesdal Storage Technologies.

NREL: Show true colors for the solar potential across the U.S.

By William L. Driscoll

Nearly all of the U.S. has at least 70% of the solar potential of land in the desert Southwest, according to government data. There is no dramatic drop-off in solar potential as you move away from the desert Southwest, as you would think from the federal map at left.

We need a new federal map to reflect solar’s true potential across the U.S.—such as the map at right, whose color scheme accurately reflects the data.

Images matter, because they shape public opinion. Someone who thinks their region has pitiful solar potential is unlikely to install rooftop solar. Solar installers working hard nationwide to transition our grid to renewables deserve support from the National Renewable Energy Laboratory, which publishes the map at left. NREL should update its map to replace its misleading colors with accurate colors.

For example, data from NREL’s key, at the bottom right of its map, show that global horizontal solar irradiance in the two northern bands is 70% of that in the two sunniest Southwest bands (4.00 kWh/m2/day versus 5.75 kWh/m2/day). That’s indicated by the moderately intense red colors at the top of the map at right, which was prepared by the author. But the pale yellows at the top of NREL’s map are nowhere close to 70% of the intensity of its colors for the Southwest.

NREL’s solar irradiance maps date back at least as far as 2009, when dramatizing the most promising regions for solar may have been appropriate. Back then, solar was expensive, and maximizing the revenue from every solar panel may have been an important consideration. But now that solar is inexpensive, it’s vital to see solar’s potential in every part of the country.

The map at right starts with pure red for the Southwestern band with the highest irradiance. The map incrementally adds more white, to create a less intense shade of red, for each lower-irradiance band, on a scale where zero irradiance would be represented by pure white. Because even the northernmost two bands have 70% of the irradiance of the far Southwestern band, their colors are deep pinkish reds that are about 70% as intense as pure red. And generally, the map appears red, because there’s substantial solar potential everywhere.

NREL is funded by taxpayers through the U.S. Department of Energy. NREL’s mission is to advance the science of renewable energy technologies, yet its map at left above is a funhouse mirror caricature of science. It’s time for NREL to fix this map.

As for the term “global horizontal solar irradiance,” that measure counts all solar radiation reaching the earth, whether directly from the sun or after passing through clouds.

Photoshop made this possible

To create the map at right, NREL’s map at left was first imported into Photoshop. The deep violet red in the lower left of NREL’s map was replaced with pure red, specified in Photoshop as R = 255, G = 0, B = 0 (RGB stands for red, green, blue).

This pure red color was used to represent 5.87 kWh/m2/day, because the key defines the deep violet red band as having global horizontal solar irradiance greater than or equal to 5.75 kWh/m2/day, and the other bands represent a range of 0.25 kWh/m2/day.

For the band next to the “maximum” band, 5.62 is the approximate midpoint of the range of 5.50 to 5.75. Thus, the ratio of the second band’s irradiance to the first band’s irradiance is 5.62/5.87, or 96%. In Photoshop, to select a shade of red that is 96% as intense as pure red, a color was selected that is 4% of the way from pure red to pure white. That color happens to be R = 255, G = 11, B = 11. Those values are based on the values for pure white (R = 255, G = 255, and B = 255), and the calculation that 11/255 is about 4%.

The same process was followed for each subsequent color band, using data from NREL’s key to transform each NREL color band into a “true color” that accurately reflects the NREL data.

How Biden could turn TVA toward clean energy—an interview with campaign leaders

By William Driscoll

Two leaders of a citizens movement calling on President Biden to transition TVA to clean energy describe their campaign, in this interview.

Biden can appoint six of the nine board members for the federally owned utility by May 2022, to fill vacancies and replace members whose terms expire. These appointments, subject to Senate confirmation, would achieve a board majority.

The new board would then need to engage with TVA’s decision-making, say the two campaign leaders, to reverse the utility’s current plans to invest in 1.5 gigawatts of new gas generation, and transition to clean energy.

Campaign coordinator Brianna Knisley of Appalachian Voices joined Daniel Tait, chief operating officer of Energy Alabama, to talk about the road ahead. The interview has been edited and condensed.

Q: Tell me about your campaign.

Brianna Knisley: The Tennessee Valley energy democracy movement formed out of a listening project in 2019, when we visited 13 communities in the TVA footprint to get a better understanding of what people wanted for their energy future, and how they want their public power system to work. We heard that people want a TVA that is more democratic, with a cleaner power supply, and that treats ratepayers in the valley fairly. TVA needs to have a target for zero emissions, and invest in energy efficiency, distributed generation and community solar.

We also want to see TVA strengthen its commitment to safe high-quality jobs. TVA has some work to do around protecting coal ash cleanup workers, and also ending harmful practices around contracting out good, full-time jobs.

TVA has operated more like a corporate investor-owned utility since 2005, when its board structure changed quite a bit. And we think TVA needs to get back to acting more like a public power provider, and one that is democratically controlled by ratepayers.

For the Tennessee Valley energy democracy movement, we use the term movement because it’s not a formal coalition. We don’t have groups formally signed on to a set of agreements. More than a dozen organizations participate—including Energy Alabama, Appalachian Voices, Statewide Organizing for Community Empowerment, and Tennessee Sunrise—as well as some grassroots and labor-focused groups, and also activists across the region. I serve as a co-convener, along with some other folks.

Q: What is the current TVA board’s stance on renewable energy?

Daniel Tait: Aside from a couple of board members that are relatively new—so we reserve judgment on those particular board members—the rest of the board members basically just defer almost everything to the management. The board has signed off on the destruction of energy efficiency programs, and small-scale renewable programs. The existing TVA board has definitely not shown any indication that it is willing to move aggressively on renewables or climate.

Q: Have you seen any signs that President Biden intends to appoint TVA board members who favor clean energy?

Daniel Tait: To meet the scale of the challenge we face as a nation, around the energy transition, really will take the Biden Administration being a little bit more aggressive than administrations have been in the past, including the Obama Administration, to be frank, about making sure that TVA’s board members are prioritized. So far, we haven’t really seen that out of the Biden Administration. We’d like to see more thought and aggressiveness in terms of the timeline from the Administration. This is a really important issue, with 1.5 gigawatts of new gas proposed from TVA, which is clearly in conflict with the Biden Administration’s executive order on net zero carbon emissions by 2035. You know, we need to act now. Having a TVA board that is willing and technically able to hold TVA management accountable is something we haven’t had. And we desperately will need new board members.

Brianna Knisley: The other priority we have is that we need TVA board members who come from environmental justice and racial justice backgrounds, who can represent labor interests, and unions that work at TVA. And, of course we need folks who can work towards climate justice as well. Historically the board has been mostly white; you see a lot of big business executives and folks that represent Chambers of Commerce. And, you know, we want to see folks with energy backgrounds and energy worker experience on the board as well.

Q: Can you say a bit more about TVA’s plans for new fossil or renewable generation?

Daniel Tait: Since Biden was sworn in, TVA has proposed nothing but new fossil fuel generation, which is not just the antithesis of the executive order, but also is a really bad economic, environmental, and social choice. It comes off as a kind of a direct challenge to the administration. They have a proposal out right now, for two 750-megawatt gas peaking plants, one in Kentucky, one in Alabama, for 1.5 gigawatts total.

This was particularly egregious, from my standpoint as a previous member of the committee that advised on TVA’s long-range resource plan, because when we went through that process, there was one run of the model where we said, let’s take off the restrictions on energy efficiency and demand response and see what happens. And lo and behold, when TVA’s model had those restrictions taken off, the model selected a lot more energy efficiency, which displaced gas. So that was pretty eye opening, that energy efficiency and demand response were the most cost-effective ways to make sure that TVA did not keep doubling down on fossil fuel infrastructure. And it’s also good for consumers in terms of lowering their bills.

Brianna Knisley: TVA also intends to prepare an environmental impact statement for advanced nuclear reactors in Oak Ridge, totaling up to 800 megawatts. They’re actually proposing a park that would contain one or more nuclear reactors.

Q: What about TVA’s announcement that it plans to add “up to 10 gigawatts” of solar power by 2040, and its resource plans generally?

Daniel Tait: Oh, absolutely. “Up to” is the operative phrase. They have been using that as a qualifier for some time, but they don’t have any concrete plans actually develop that much. We haven’t seen any board materials or budget materials showing that they’re actually putting their money where their mouth is on that stuff, but just kind of putting it in press releases. They have shuttered a few coal plants down in the last few years, but they still have a few running. Of course, now they’re trying to replace some older gas with new gas. So you know, it could make them cleaner, you know, but will it get them close to 100%? No.

In terms of what a clean energy grid looks like, for generating capacity and storage, frankly, we don’t really know the answer to that. The upcoming integrated resource plan will have to model some scenarios of net zero by 2050, at the absolute latest, and it will need to have other benchmarks like 80% by 2030, or 100% by 2035—different types of benchmarks like that to see what TVA’s grid would look like under those types of scenarios.

In Alabama, where I live, Alabama Power doesn’t even file an integrated resource plan; it just files a two-page summary and then hides all the rest. So, by comparison, TVA, which actually has an open process, looks pretty dang good. That said, as a previous member of the resource plan committee, I can say there’s a lot of power that TVA wields over the working group.

I think would be instructive to see what an independent third party could come up with, and you’re starting to see some other intervenors—like with Duke Energy in North Carolina—some of the intervenors ran their own integrated resource plan, and submitted that as part of their testimony in that docket, and it’s very different from what Duke is proposing. Something like that could be instructive here for TVA.

Q: What does the interest of Memphis in exiting TVA indicate about the potential for lower cost renewable generation in the TVA region?

Daniel Tait: It’s complex, but TVA’s high wholesale power costs are driven by lots of debt that it’s carrying from failed nuclear investments in the ‘70s and ‘80s, coal plants that it refuses to shutter, and historic under-investment in energy efficiency and demand response. These bad decisions and under-investment have driven the wholesale power cost to uncompetitive levels compared to many of its neighbors.

You’ve probably seen the studies that show hundreds of million dollars could be saved by the Memphis municipal utility, by leaving the TVA. It says there’s a lot of opportunity, right? TVA could put downward pressure on the wholesale power rate by doing a lot of things I just mentioned. Not only could it save that kind of money for Memphis, but all of the rest of the local power companies in the valley could also then get massive amounts of savings too—probably billions of dollars in savings. Brianna Knisley: We all just want to see TVA live up to the ideals that were espoused in the original TVA Act, and become the living lab that we all think it should be. TVA could be a model for how utilities can transition rapidly towards clean energy in a way that is equitable, and supports workers. TVA could definitely do that with the support of the federal government. There’s just a widespread disappointment that TVA has been resisting that transition for unknown reasons. TVA has the ability to do it.

‘Waze’ for power lines would unlock 500 GW of renewables projects

By William Driscoll

U.S. utilities could use three technologies to increase the utilization of transmission lines, enabling 500 GW of renewables projects to win interconnection approval, say industry veterans Jigar Shah and Rob Gramlich, in an op-ed published by Utility Dive.

Three transmission technologies have been implemented in “a matter of weeks and months” to increase transmission utilization in many parts of the world, say the authors. The technologies are shown in this image from the WATT Coalition:

Without these technologies, 500 GW of solar and wind projects “are currently stuck in transmission queues, forcing developers to wait as long as 900 days to get interconnected to the grid,” said the experts.

The Federal Energy Regulatory Commission (FERC) should create investment incentives for utilities to implement the advanced transmission technologies, wrote Shah, who is president of Generate Capital, and Gramlich, who is president of Grid Strategies and the point of contact for the WATT Coalition.

Without such incentives, utilities will favor new transmission lines, on which they can earn a guaranteed rate of return on the massive investments required. “Rather than encouraging electric utilities to spend more,” said Shah and Gramlich, “the incentive for grid-enhancing technologies must instead reward utilities for more efficiently using what we have already paid for.”

Thirteen U.S. Senators wrote to FERC last month, asking the commission to create performance-based incentives for utilities to improve transmission capacity and efficiency. They noted that the Energy Policy Act of 2005 directed FERC to “implement transmission rates that improve reliability and reduce the cost of power.” The Senators favor storage as transmission, in addition to the three technologies promoted by the WATT Coalition.

Grid operator Southwest Power Pool (SPP) has validated one of the three technologies, advanced topology, through a back-testing simulation of 20 actual instances of “congestion/overloads.” A joint presentation by SPP, The Brattle Group and Newgrid described advanced topology as “Waze for the transmission grid”–moving power along less-congested lines–with sample results shown in this diagram:

SPP found that if it had used advanced topology in the 20 cases studied, power flow would have been reduced on the constrained transmission line by an average of 26%, and by at least 10% in each case.

The U.S. Department of Energy described the technology of dynamic line ratings for transmission lines, by comparing it to the widely used static line ratings:

  • The maximum power flow capacity on a transmission line is limited by heating considerations, to maintain safe and reliable operating conditions. These static line ratings (SLRs) are usually calculated using conservative assumptions about the transmission-line operating environment, producing an inflexible constraint that does not take advantage of changing or favorable environmental conditions (e.g., wind cooling) that allow for greater transmission usage. DLR is a blanket term for the many different technologies and methodologies for determining conductor thermal ratings in a more-dynamic fashion using improved, more granular, or real-time data. At its core, DLR systems help system operators determine the prevailing current carrying capacity limits of transmission lines to relax constraints based on SLRs.

To describe the technology of advanced power flow control, the WATT Coalition draws a comparison with ordinary power flow control:

  • Power flow control is a set of technologies that push or pull power away from overloaded lines and onto underutilized corridors within the existing transmission network. Advanced power flow control provides this same function with advanced features such as the ability to be quickly deployed, easily scaled to meet the size of the need, or redeployed to new parts of the grid when no longer needed in the current location.

Members of the WATT Coalition include AmpacimonLineVision, IncLindsey ManufacturingNewGridSmartWires, and WindSim Americas Inc. The coalition’s acronym stands for “working for advanced transmission technology.”

Hot roofs above row house bedrooms cause sleep deprivation; a public health law is needed

Row houses in Baltimore. Black roofs above bedrooms get as hot as 150 degrees.

People who sleep in a top-floor bedroom under a black asphalt roof are likely to lose sleep on summer nights due to heat from the roof, with serious health consequences.  Technically, the fix is simple—coat every black asphalt roof with a white coating—but progress toward that goal is slow.  The answer: a public health law requiring white coating of hot roofs in every city with this problem.

The issue: black asphalt roofs get really hot, keeping people from sleeping well, causing dangerous health problems

Black asphalt roofs, which are common on Northeast urban row houses (townhouses), “can reach temperatures of 150°F or more in the summer sun,” reports the U.S. Department of Energy.  With or without air conditioning, a roof that hot above your bedroom will radiate heat at you all night long.

And people can’t sleep well when it’s too hot.  A research study using data reported by 765,000 people over 10 years found that “increases in nighttime temperatures amplify self-reported nights of insufficient sleep.”

Losing sleep is far worse than a nuisance.  “People make cognitive errors that matter when they sleep badly, whether crashing vehicles or making poor decisions in the workplace,” said UC Berkeley professor Solomon Hsiang in response to the study, as reported by Bloomberg.  He added, “Students learn poorly when they don’t sleep, and consistent lack of sleep harms people’s health.”

And in a heat wave, hot roofs can result in death: in Chicago’s 1995 heat wave, those at increased risk included those “who lived on the top floor of a building (odds ratio, 4.7),” according to a New England Journal of Medicine article.

The technically easy solution:  white roof coating of asphalt roofs

Any roofing firm can apply an “elastomeric” white roof coating to a black asphalt roof, which can reduce a roof’s temperature on a 90-degree day from 150°F to 95°F.  (“Elastomeric” means the coating will stretch with the roof on hot days, and contract with the roof on cold days.)  A homeowner who can safely get up on their own roof, with tools and supplies, can also do the job.  The cost is modest, since the job is relatively small: clean, patch, prime, and apply the finish coat.

But progress in getting black asphalt roofs coated white is slow.  For example, people in Philadelphia have been talking for a decade about this problem, but the Google Maps satellite view of the city shows mostly black roofs, while the roofs that aren’t black are generally gray—a color that provides only about half the cooling benefit of a white roof.

How to persuade landlords to apply white roof coating to black asphalt roofs?

Landlords are under no pressure to apply a white roof coating to their properties to improve their tenants’ health.  Cities could institute a public health measure limiting the temperature of bedroom ceilings, and requiring white roof coating if that temperature is exceeded.  Such a law could presume that black roofs exceed that temperature (and gray roofs as well, if data showed that to be the case).  Then, if a landlord failed to coat the roof white—or provide data proving the bedroom ceilings remained cool enough—the city could do it for the landlord and bill the landlord via the property tax bill.  (In my city, letting your grass grow tall is considered a public health problem, and if you don’t cut your grass the city will cut it for you, and bill you for the work.  So a public health law to prevent sleep deprivation is a no-brainer.) 

Air conditioning is not enough

With or without air conditioning, bedroom ceiling temperatures reached 90 degrees and higher in row houses during a Philadelphia heat wave. Any ceiling above 91 degrees (human skin temperature) will radiate heat to humans, and any ceiling only several degrees below that temperature will make it difficult for humans to radiate heat to the ceiling.

Bedroom air temperatures measured in that study climbed to the 80s/90s in all houses with black tar roofs, with or without air conditioning.

A precedent—recognizing heat as a public health hazard

In Maryland, Montgomery County Councilman Tom Hucker has introduced a bill to make working air conditioning a requirement for all rental units in the county (Bill 24-19). This proposal recognizes that heat is a public health hazard.  Even with air conditioning, a hot tar roof over a row house will radiate heat into bedrooms all night long—and some tenants will limit their use of air conditioning because they can’t afford the bills. Cooling the roof will dramatically reduce heat exposure.


Solar on schools advances with open source contracting

With every new solar-on-schools contract, more people learn how it’s done, share what they know, and make it easier for neighboring school districts to follow the same path. U.S. schools could host up to 30 gigawatts of solar (that’s 30,000 megawatts).

School board members raised legitimate concerns about a proposal to put solar on five schools in Arlington, Virginia. What would teachers and parents think, for example, if the school system put resources into solar that could instead be used to increase teacher salaries or buy new textbooks?  

The fact that a solar power purchase agreement (PPA) would have no capital cost, and could save on operating costs, met those concerns. After a meticulous procurement process, the school board voted unanimously to approve the selected PPA contract, largely because it would save the school district an estimated $4 million in operating costs over the 25-year contract. Each of the five schools will have an energy dashboard for teaching purposes.

The 2.5 megawatts of solar that will result—the largest solar-on-schools project in northern Virginia—illustrates how such decisions could ultimately yield up to 30 gigawatts of solar on U.S. public schools. (That would be the result if all 98,000 public schools installed 0.3 megawatts of rooftop solar—the average system size in 2017.)  

Arlington managed its own procurement, learning from the previous experience of neighboring jurisdictions, and hiring individual consultants as needed. Another path is illustrated by Washington, DC—across the Potomac River from Arlington—which contracted with a solar development firm to help manage an 11.8 megawatt solar procurement.

Arlington’s school district made a number of smart moves, in the view of this advocate and participant, in getting across the finish line. Here are the steps they took.

Find a team to drive the process

In Arlington’s case, the superintendent of schools had expressed interest in getting solar on all schools. That support paved the way for the school system’s energy manager to work with procurement and finance staff to explore a solar PPA, once the cost of solar became attractive. School board members were kept informed of the process.  

If instead school board members drive the process while staff are reluctant, it could be helpful to hire a solar development firm to help move things along.

Inform school board members that solar is no longer expensive

Many people outside the solar industry assume that solar is still expensive. Solar advocates focused on the newly attractive cost of solar in discussions with school board members. A former elected official played an important role here, as he was trusted by school board members. 

Eliminate legal uncertainties

Legal counsel for the school system determined that an amendment was needed to the purchasing resolution to create the authority to enter into a power purchase agreement.

School board members were reassured to see a provision in the amended resolution that, once a request for proposals was issued and bids were received, they would have the final say on whether a contract would be signed. With that guarantee, all five school board members voted yes on the amended resolution.  

Staff then had the go-ahead to issue a request for proposals (RFP).  

Get a unanimous school board vote at the “let’s get started” stage

No firm wants to do the time-consuming work of preparing a bid, only to hear that the prospective buyer decided not to buy after all. The Arlington School Board’s unanimous vote on the purchasing resolution helped give confidence to solar installation firms that one winning firm would indeed be awarded a contract.

Prepare an RFP that protects taxpayers 

Arlington’s RFP attracted price competition among bidders by setting a healthy project size of five schools, and providing qualified bidders with structural, electrical, and roofing information for each school. This meant that bidders would not need to expend resources obtaining this information.  

Each firm that submitted a bid was required to demonstrate relevant experience, state its project financing plan, provide audited financial statements, and commit to operate and maintain the solar installations. The RFP required racking made of non-ferrous metal, and favored a ballasted racking system. It included several other roof-related provisions, and required an option, after the 25-year contract expired, to buy the systems at the market price. 

Unlike some PPAs that begin with a modest initial price per kilowatt-hour that escalates over time, Arlington’s RFP called for a fixed price for electricity over the contract term. A fixed price, explained Arlington Public Schools (APS) Energy Manager Cathy Lin, gives the school system stability in managing its energy budget over the term of the contract.

To help prepare the RFP, school system staff called on engineering, structural, electrical, and legal consultants. Ms. Lin noted that APS staff also found two RFPs previously issued in neighboring Maryland to be helpful—one issued by Montgomery County, and another by the state’s Department of Transportation. She added that a solar PPA template prepared by the National Renewable Energy Laboratory also came in handy (Commercial PPA Version 1.1). 

Go through a routine procurement process

Arlington held a bidder’s meeting, provided an opportunity for site inspections at the selected schools, answered questions from prospective bidders, and revised the RFP as needed. Six bids were received, of which four met all bid requirements.  

Once the bids were in, APS staff again brought in consultants with engineering, structural, electrical, and legal expertise. Three bidders were invited to make presentations: Ameresco, Sun Tribe Solar, and WGL Energy Systems. Staff recommended to the school board a draft contract from Sun Tribe Solar of Charlottesville, Virginia, based on the firm’s reputation with similar installations, as well as its site designs, operations plan, and engineering and financing approach.

Cross the finish line

School board members were advised that the solar PPA’s fixed price of 7.96 cents per kWh, for net metered electricity, would save the school district an estimated $4 million over the 25-year contract term, based on a projected 2.5% annual price increase for utility-provided electricity.  

Arlington school board members voted unanimously to sign the contract. That unanimous vote will be helpful in persuading firms to bid for the next round of solar on more APS schools.

Pay it forward

APS has posted its purchasing resolution,RFPcontract, and related documents online for all to see, following its routine procurement practice.  

Other school districts—as well as owners of commercial and industrial buildings—may now review these documents, just as APS reviewed the documents of those with earlier experience.

Ideally, coordinate with other school districts in adding solar

Because some utilities have sought to increase fixed charges on customers who have adopted rooftop solar, it makes sense for school districts in the same state or utility service area to aim to go solar together, for increased political influence. Notably, an elected official who represents much of Arlington in the Virginia legislature attended the signing ceremony for the APS solar contract. 

Originally published in PV Magazine USA

Recover high-GWP refrigerants, favor low-GWP refrigerants to limit climate damage

Honeywell HFO-1234yf refrigerant

Image: Refrigerant Depot

By Will Driscoll

To limit climate damage from refrigerants with a high global warming potential:

  • States may require leak testing and leak repair of equipment using refrigerants, as California now requires for large equipment (see section 5 below).
  • States may also have authority to require that when equipment using refrigerant will no longer be used, that its refrigerant be recovered and either destroyed or reclaimed (recycled). A financial incentive or a refundable deposit could boost voluntary compliance.
  • Environmental groups may encourage people to choose equipment with low-GWP (global warming potential) refrigerants, such as R-1234, which has a GWP of 4 to 6 (see table below). This equipment includes vehicles, heat pumps, air conditioners, refrigerators, freezers, and dehumidifiers.

The following sections first describe various refrigerants, and then review refrigerant management policy at the global, U.S., and E.U. levels, and in California.

  1. Selected Refrigerants: Phased Out, In Use, and Under Consideration
RefrigerantGlobal Warming Potential (GWP)*,**Status
CFCsPhased out under the Montreal Protocol
HCFCsBeing phased out
HFCsWidely used
HFC: R5073300US: Were to be phased out via EPA’s 2015 and 2016 rules.*** A three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit struck down the 2015 rule.  That ruling has been appealed to the full en banc panel of the same appeals court.
HFC: R404A3260
HFC: R410A1725US: Was to be partially phased out via EPA’s 2015 and 2016 rules;*** see above.
HFC: R4071525
HFC: (R)134a1430US: Was to be phased out in light-duty vehicles via EPA’s 2015 rule, which is now in the courts—see above.
HFC: 152a (R152a)  124
HFO 1234 (R-1234)      4Now used in some vehicle air conditioners
“Natural refrigerants”: CO2 (R744) and ammonia (NH3)CO2: 1Daimler and Volkswagen are evaluating CO2 for vehicle air conditioners.****

Note: The “R” refrigerants are a blend of two different HFC compounds, except for R744 (CO2).





  1. Global Policy

The Montreal Protocol’s Kigali Amendment of 2016, which requires a global phasedown of HFCs, will enter into force on January 1, 2019:  “Under the amendment, developed countries will reduce HFC consumption beginning in 2019”:  The amendment apparently does not address HFC recovery and destruction:

  1. U.S. Policy

EPA issued two HFC phase-out regulations in 2015 and 2016.****  The “Final Rule Revising the Section 608 Refrigerant Management Regulations” made “changes to the existing requirements under Section 608 [including] … 1) Extends the requirements of the Refrigerant Management Program to cover substitute refrigerants, such as HFCs”:

A three-judge panel of the U.S. Court of Appeals for the District of Columbia Circuit ruled on August 8, 2017 that the U.S. EPA does not have authority under Clean Air Act Section 612 to regulate HFCs.  Refrigerant manufacturers and the NRDC have appealed for a rehearing of the case by a panel of all the appeals court judges of the DC Circuit (an “en banc” panel).

Prior EPA regulations require recovery of ozone-depleting refrigerants when existing equipment is removed, with the refrigerants sent out for destruction or reclamation (recycling):

The amounts recovered each year from 2000-2016 are shown here:

EPA-certified refrigerant reclaimers are shown on this list:

  1. E.U. Policy

The E.U. adopted a regulation in 2014 to phase out HFCs, and encourage refrigerant recovery and destruction at the end of a unit’s service life. (EU regulation 517/2014).  “Member States shall encourage the development of producer responsibility schemes for the recovery of fluorinated greenhouse gases and their recycling, reclamation or destruction.”

  1. California Policy

The California Air Resources Board (CARB) Refrigerant Management Program requires commercial and industrial facilities with a refrigeration system using more than 50 pounds of a high-GWP refrigerant (including HFCs) to register with CARB, to test for leaks, and if a leak is detected, to repair, retrofit or retire the equipment.  The program apparently does not address refrigerant recovery and destruction.


Arlington to add solar on five schools, for largest such procurement in Virginia

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By Will Driscoll

Arlington has solicited bids to add rooftop solar panel systems on at least five schools by 2020, for the largest solar-on-schools procurement to date in Virginia. School system staff designed the solicitation to achieve a competitive price for solar, and to avoid financial headaches such as roof repairs down the road.

The solicitation is structured to attract competition among bidders, yielding a competitive price, by:

• Specifying a larger project size of five schools (with an option for more), rather than the two schools initially envisioned; and

• Reducing the cost of bidding, by providing bidders with ready access to structural and electrical system information for each of the five schools, as well as each roof’s age, type, and warranty information.

The resulting bids will be easy to compare on price, because each bidder must set a fixed price at which it will sell solar electricity to the school system over a period of 15 to 25 years. This contrasts with many existing solar power purchase agreements that specify a starting price and an annual price increase—a more complex approach that is harder to compare across bids.*

The solar-on-schools project has been de-risked in several ways:

• Firms or teams are only eligible to bid if: 1) they have installed at least five similarly-sized projects; 2) they have operated and maintained at least five projects; and 3) they have appropriate contractor and electrical licenses.

• A bidder must state its plan for financing all stages of the project, and provide audited financial statements for the firm (which will be kept confidential).

• The selected contractor must operate and maintain the solar panel systems. (This provision is self-enforcing, since the contractor will only receive payment for the electricity that each system generates.)

• The contractor must specify a method for determining a buy-out price in case the school system chooses to terminate the contract “for convenience.”

Additional provisions address potential roof and durability issues:

• Ballasted systems are preferred, to eliminate roof penetrations that could leak.

• The use of ferrous metals, wood or plastic (e.g., in the solar panel racking system) is not permitted.

• The selected contractor must work with the obligor under any roof warranty to ensure that the warranty remains in effect.

• The contractor must repair any damage to the school caused by the system, including moisture damage.

• In the event that roof repair is needed due to aging of the existing roof, the contractor must remove the solar panel system and then replace it once the repair is completed, at no extra charge; the contractor’s price must account for this possibility.

Arlington’s solar solicitation follows an amendment to the school system’s purchasing resolution, unanimously approved by Arlington’s school board last spring, to permit the use of power purchase agreements under the requirements of Virginia’s Public-Private Educational Facilities and Infrastructure Act of 2002. (Members of Arlington 350 advocated for this resolution.)

Proposals are due from bidders in March, 2018. The school system’s purchasing resolution calls for APS to hire “qualified professionals” from outside the APS staff to review all solicited proposals. These professionals may include an architect, professional engineer, or certified public accountant.

Any rooftop solar offer recommended by the selection committee will be presented at a public hearing, and must be approved by the school board before a contract is signed, per the school system’s purchasing resolution.

Solar installations are to be completed within two years of contract award. The school system may arrange with the selected offeror for solar on additional schools. (A draft timeline from last April anticipated the installation of solar PV systems on two schools in summer 2018.)

Statewide, Virginia could produce 32 percent of its electricity from rooftop solar, according to a National Renewable Energy Laboratories report. Given the increase in solar panel efficiency, from 16 percent assumed in the report to about 20 percent now, the current opportunity is correspondingly higher: we could get 40 percent of our electricity from rooftop solar. Virginia’s approximately 2,100 public schools, with unshaded roofs ideal for low-cost commercial scale solar, represent a promising component of that potential.

Credit is due to Arlington school system staff—in the facilities engineering, purchasing, and legal departments—for their work on the 113-page solicitation, and the amendment to the purchasing resolution that preceded it.

Climate-aware citizens in other communities may find Arlington’s solicitation to be a useful model for their own solar-on-schools initiatives.

*An Arlington bidder may additionally offer, as an alternative to its fixed price, an initial price and an annual price increase, which the school system may select at its discretion.

(Photo: Arlington’s Discovery Elementary School, showing the 497-kilowatt rooftop solar system in a satellite view.  Source: Google Maps.)