Thermal storage may bring back baseboard heating

By WLBZ


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When it comes to heating sources, a lot of homeowners won't consider electric heat. But a new company in Saco is hoping to change that.

Thermal Energy Storage of Maine is promoting electric thermal storage systems. They say the devices can provide as much as sixty percent of a home's heating needs, and do it for less money than oil.

The units are filled with heavy ceramic bricks, sandwiched between electric coils. They heat up to 1,100 degrees, and then radiate the heat for hours.

Sam Zaitlin, President of Thermal Energy Storage, says the devices are designed to use what is called off-peak power. That means they heat up at night when electricity is much cheaper.

Special arrangements with the electric company are needed for that, but Zaitlin says both Bangor Hydro and Central Maine Power already offer the service. He says the units are common in a number of other states, in Canada and in Europe, but are not well known in Maine.

He says this can be another way to reduce the state's dependence on foreign oil.

"Right now our game plan is to offer these units, beginning the first quarter of 2011 with a locked in electricity price in the range, the equivalent range of 2.45 to 250 a gallon oil. Locked in two years at a time," said Zaitlin.

Zaitlin says the electric heating units are an ideal companion to Maine's growing number of wind farms. He says the state's current energy plan calls for three thousand megawatts of wind power by 2020.

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Barakah Unit 1 reaches 100% power as it steps closer to commercial operations, due to begin early 2021

Barakah Unit 1 100 Percent Power signals the APR-1400 reactor delivering 1400MW of clean baseload electricity to the UAE grid, advancing decarbonisation, reliability, and Power Ascension Testing milestones ahead of commercial operations in early 2021.

 

Key Points

The milestone where Unit 1 reaches full 1400MW output to the UAE grid, providing clean, reliable baseload electricity.

✅ Delivers 1400MW from a single generator to the UAE grid

✅ Enables clean, reliable baseload power with zero operational emissions

✅ Completes key Power Ascension Testing before commercial operations

 

The Emirates Nuclear Energy Corporation, ENEC, has announced that its operating and maintenance subsidiary, Nawah Energy Company, Nawah, has successfully achieved 100% of the rated reactor power capacity for Unit 1 of the Barakah Nuclear Energy Plant. This major milestone, seen as a crucial step in Abu Dhabi towards completion, brings the Barakah plant one step closer to commencing commercial operations, scheduled in early 2021.

100% power means that Unit 1 is generating 1400MW of electricity from a single generator connected to the UAE grid for distribution. This milestone makes the Unit 1 generator the largest single source of electricity in the UAE.

The Barakah Nuclear Energy Plant is the largest source of clean baseload electricity in the country, capable of providing constant and reliable power in a sustainable manner around the clock. This significant achievement accelerates the decarbonisation of the UAE power sector, while also supporting the diversification of the Nation’s energy portfolio as it transitions to cleaner electricity sources, similar to the steady development in China of nuclear energy programs now underway.

The accomplishment follows shortly after the UAE’s celebration of its 49th National Day, providing a strong example of the country’s progress as it continues to advance towards a sustainable, clean, secure and prosperous future, having made the UAE the first Arab nation to open a nuclear plant as it charts this path. As the Nation looks towards the next 50 years of achievements, the Barakah plant will generate up to 25 percent of the country’s electricity, while also acting as a catalyst of the clean carbon future of the Nation.

Mohamed Ibrahim Al Hammadi, Chief Executive Officer of ENEC said: "We are proud to deliver on our commitment to power the growth of the UAE with safe, clean and abundant electricity. Unit 1 marks a new era for the power sector and the future of the clean carbon economy of the Nation, with the largest source of electricity now being generated without any emissions. I am proud of our talented UAE Nationals, working alongside international experts who are working to deliver this clean electricity to the Nation, in line with the highest standards of safety, security and quality." Nawah is responsible for operating Unit 1 and has been responsible for safely and steadily raising the power levels since it commenced the start-up process in July, and connection to the grid in August.

Achieving 100% power is one of the final steps of the Power Ascension Testing (PAT) phase of the start-up process for Unit 1. Nawah’s highly skilled and certified nuclear operators will carry out a series of tests before the reactor is safely shut down in preparation for the Check Outage. During this period, the Unit 1 systems will be carefully examined, and any planned or corrective maintenance will be performed to maintain its safety, reliability and efficiency prior to the commencement of commercial operations.

Ali Al Hammadi, Chief Executive Officer of Nawah, said: "This is a key achievement for the UAE, as we safely work through the start-up process for Unit 1 of the Barakah plant. Successfully reaching 100% of the rated power capacity in a safe and controlled manner, undertaken by our highly trained and certified nuclear operators, demonstrates our commitment to safe, secure and sustainable operations as we now advance towards our final maintenance activities and prepare for commercial operations in 2021." The Power Ascension Testing of Unit 1 is overseen by the independent national regulator – the Federal Authority for Nuclear Regulation (FANR), which has conducted 287 inspections since the start of Barakah’s development. These independent reviews have been conducted alongside more than 40 assessments and peer reviews by the International Atomic Energy Agency, IAEA, and World Association of Nuclear Operators, WANO, reflecting milestones at nuclear projects worldwide that benchmark safety and performance.

This is an important milestone for the commercial performance of the Barakah plant. Barakah One Company, ENEC’s subsidiary in charge of the financial and commercial activities of the Barakah project signed a Power Purchase Agreement, PPA, with the Emirates Water and Electricity Company, EWEC, in 2016 to purchase all of the electricity generated at the plant for the next 60 years. Electricity produced at Barakah feeds into the national grid in the same manner as other power plants, flowing to homes and business across the country.

This milestone has been safely achieved despite the challenges of COVID-19. Since the beginning of the global pandemic, ENEC, and subsidiaries Nawah and Barakah One Company, along with companies that form Team Korea, including Korea Hydro & Nuclear Power, with KHNP’s work in Bulgaria illustrating its global role, have worked closely together, in line with all national and local health authority guidelines, to ensure the highest standards for health and safety are maintained for those working on the project. ENEC and Nawah’s robust business continuity plans were activated, alongside comprehensive COVID-19 prevention and management measures, including access control, rigorous testing, and waste water sampling, to support health and wellbeing.

The Barakah Nuclear Energy Plant, located in the Al Dhafra region of the Emirate of Abu Dhabi, is one of the largest nuclear energy new build projects in the world, with four APR-1400 units. Construction of the plant began in 2012 and has progressed steadily ever since. Construction of Units 3 and 4 are in the final stages with 93 percent and 87 percent complete respectively, benefitting from the experience and lessons learned during the construction of Units 1 and 2, while the construction of the Barakah Plant as a whole is now more than 95 percent complete.

Once the four reactors are online, Barakah Plant will deliver clean, efficient and reliable electricity to the UAE grid for decades to come, providing around 25 percent of the country’s electricity and, as other nations like Bangladesh expand with IAEA assistance, reinforcing global decarbonisation efforts, preventing the release of up to 21 million tons of carbon emissions annually – the equivalent of removing 3.2 million cars off the roads each year.

 

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A new nuclear reactor in the U.S. starts up. It's the first in nearly seven years

Vogtle Unit 3 Initial Criticality marks the startup of a new U.S. nuclear reactor, initiating fission to produce heat, steam, and electricity, supporting clean energy goals, grid reliability, and carbon-free baseload power.

 

Key Points

Vogtle Unit 3 Initial Criticality is the first fission startup, launching power generation at a new U.S. reactor.

✅ First new U.S. reactor to reach criticality since 2016

✅ Generates carbon-free baseload power for the grid

✅ Faced cost overruns and delays during construction

 

For the first time in almost seven years, a new nuclear reactor has started up in the United States.

On Monday, Georgia Power announced that the Vogtle nuclear reactor Unit 3 has started a nuclear reaction inside the reactor as part of the first new reactors in decades now taking shape at the plant.

Technically, this is called “initial criticality.” It’s when the nuclear fission process starts splitting atoms and generating heat, Georgia Power said in a written announcement.

The heat generated in the nuclear reactor causes water to boil. The resulting steam spins a turbine that’s connected to a generator that creates electricity.

Vogtle’s Unit 3 reactor will be fully in service in May or June, Georgia Power said.

The last time a nuclear reactor reached the same milestone was almost seven years ago in May 2016 when the Tennessee Valley Authority started splitting atoms at the Watts Bar Unit 2 reactor in Tennessee, Scott Burnell, a spokesperson for the Nuclear Regulatory Commission, told CNBC.

“This is a truly exciting time as we prepare to bring online a new nuclear unit that will serve our state with clean and emission-free energy for the next 60 to 80 years,” Chris Womack, CEO of Georgia Power, said in a written statement. 

Including the newly turned-on Vogtle Unit 3 reactor, there are currently 93 nuclear reactors operating in the United States and, collectively, they generate 20% of the electricity in the country, although a South Carolina plant leak recently showed how outages can sideline a unit for weeks.

Nuclear reactors, which help combat global warming and support net-zero emissions goals, generate about half of the clean, carbon-free electricity generated in the U.S.

Most of the nuclear power reactors in the United States were constructed between 1970 and 1990, but construction slowed significantly after the accident at Three Mile Island near Middletown, Pennsylvania, on March 28, 1979, even as interest in next-gen nuclear power has grown in recent years. From 1979 through 1988, 67 nuclear reactor construction projects were canceled, according to the U.S. Energy Information Administration.

However, because nuclear energy is generated without releasing carbon dioxide emissions, which cause global warming, the increased sense of urgency in responding to climate change has given nuclear energy a chance at a renaissance as atomic energy heats up again globally.

The cost associated with building nuclear reactors is a major barrier to a potential resurgence in nuclear energy, however, even as nuclear generation costs have fallen to a ten-year low. And the new builds at Vogtle have become an epitome of that charge: The construction of the two Vogtle reactors has been plagued by cost overruns and delays.
 

 

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More pylons needed to ensure 'lights stay on' in Scotland, says renewables body

Scottish Renewable Grid Upgrades address outdated infrastructure, expanding transmission lines, pylons, and substations to move clean energy, meet rising electricity demand, and integrate onshore wind, offshore wind, and battery storage across Scotland.

 

Key Points

Planned transmission upgrades in Scotland to move clean power via new lines and substations for a low-carbon grid.

✅ Fivefold expansion of transmission lines by 2030

✅ Enables onshore and offshore wind integration

✅ New pylons, substations, and routes face local opposition

 

Renewable energy in Scotland is being held back by outdated grid infrastructure, industry leaders said, with projects stuck on hold underscoring their warning that new pylons and power lines are needed to "ensure our lights stay on".

Scottish Renewables said new infrastructure is required to transmit the electricity generated by green power sources and help develop "a clean energy future" informed by a broader green recovery agenda.

A new report from the organisation - which represents companies working across the renewables sector - makes the case for electricity infrastructure to be updated, aligning with global network priorities identified elsewhere.

But it comes as electricity firms looking to build new lines or pylons face protests, with groups such as the Strathpeffer and Contin Better Cable Route challenging power giant SSEN over the route chosen for a network of pylons that will run for about 100 miles from Spittal in Caithness to Beauly, near Inverness.

Scottish Renewables said it is "time to be upfront and honest" about the need for updated infrastructure.

It said previous work by the UK National Grid estimated "five times more transmission lines need to be built by 2030 than have been built in the past 30 years, at a cost of more than £50bn".

The Scottish Renewables report said: "Scotland is the UK's renewable energy powerhouse. Our winds, tides, rainfall and longer daylight hours already provide tens of thousands of jobs and billions of pounds of economic activity.

"But we're being held back from doing more by an electricity grid designed for fossil fuels almost a century ago, a challenge also seen in the Pacific Northwest today."

Investment in the UK transmission network has "remained flat, and even decreased since 2017", echoing stalled grid spending trends elsewhere, the report said.

It added: "We must build more power lines, pylons and substations to carry that cheap power to the people who need it - including to people in Scotland.

"Electricity demand is set to increase by 50% in the next decade and double by mid-century, so it's therefore wrong to say that Scottish households don't need more power lines, pylons and substations.

Renewable energy in Scotland is being held back by outdated grid infrastructure, industry leaders said, as they warned new pylons and power lines are needed to "ensure our lights stay on".

Scottish Renewables said new infrastructure is required to transmit the electricity generated by green power sources and help develop "a clean energy future".

A new report from the organisation - which represents companies working across the renewables sector - makes the case for electricity infrastructure to be updated.

But it comes as electricity firms looking to build new lines or pylons face protests, with groups such as the Strathpeffer and Contin Better Cable Route challenging power giant SSEN over the route chosen for a network of pylons that will run for about 100 miles from Spittal in Caithness to Beauly, near Inverness.

Scottish Renewables said it is "time to be upfront and honest" about the need for updated infrastructure.

It said previous work by the UK National Grid estimated "five times more transmission lines need to be built by 2030 than have been built in the past 30 years, at a cost of more than £50bn".

The Scottish Renewables report said: "Scotland is the UK's renewable energy powerhouse. Our winds, tides, rainfall and longer daylight hours already provide tens of thousands of jobs and billions of pounds of economic activity.

"But we're being held back from doing more by an electricity grid designed for fossil fuels almost a century ago."

Investment in the UK transmission network has "remained flat, and even decreased since 2017", the report said.

It added: "We must build more power lines, pylons and substations to carry that cheap power to the people who need it - including to people in Scotland.

"Electricity demand is set to increase by 50% in the next decade and double by mid-century, so it's therefore wrong to say that Scottish households don't need more power lines, pylons and substations.

"We need them to ensure our lights stay on, as excess solar can strain networks in the same way consumers elsewhere in the UK need them.

"With abundant natural resources, Scotland's home-grown renewables can be at the heart of delivering the clean energy needed to end our reliance on imported, expensive fossil fuel.

"To do this, we need a national electricity grid capable of transmitting more electricity where and when it is needed, echoing New Zealand's electricity debate as well."

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Nick Sharpe, director of communications and strategy at Scottish Renewables, said the current electricity network is "not fit for purpose".

He added: "Groups and individuals who object to the construction of power lines, pylons and substations largely do so because they do not like the way they look.

"By the end of this year, there will be just over 70 months left to achieve our targets of 11 gigawatts (GW) offshore and 12 GW onshore wind.

"To ensure we maximise the enormous socioeconomic benefits this will bring to local communities, we will need a grid fit for the 21st century."

 

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Alberta is a powerhouse for both green energy and fossil fuels

Alberta Renewable Energy Market is accelerating as wind and solar prices fall, corporate PPAs expand, and a deregulated, energy-only system, AESO outlooks, and TIER policy drive investment across the province.

 

Key Points

An open, energy-only Alberta market where wind and solar growth is driven by corporate PPAs, AESO outlooks, and TIER.

✅ Energy-only, deregulated grid enables private investment

✅ Corporate PPAs lower costs and hedge power price risk

✅ AESO forecasts and TIER policy support renewables

 

By Chris Varcoe, Calgary Herald

A few things are abundantly clear about the state of renewable energy in Alberta today.

First, the demise of Alberta’s Renewable Electricity Program (REP) under the UCP government isn’t going to see new projects come to a screeching halt.

In fact, new developments are already going ahead.

And industry experts believe private-sector companies that increasingly want to purchase wind or solar power are going to become a driving force behind even more projects in Alberta.

BluEarth Renewables CEO Grant Arnold, who spoke Wednesday at the Canadian Wind Energy Association conference, pointed out the sector is poised to keep building in the province, even with the end of the REP program that helped kick-start projects and triggered low power prices.

“The fundamentals here are, I think, quite fantastic — strong resource, which leads to really competitive wind prices . . . it’s now the cheapest form of new energy in the province,” he told the audience.

“Alberta is in a fundamentally good place to grow the wind power market.”

Unlike other provinces, Alberta has an open, deregulated marketplace, which create opportunities for private-sector investment and renewable power developers as well.

The recent decision by the Kenney government to stick with the energy-only market, instead of shifting to a capacity market, is seen as positive for Alberta's energy future by renewable electricity developers.

There is also increasing interest from corporations to buy wind and solar power from generators — a trend that has taken off in the United States with players such as Google, General Motors and Amazon — and that push is now emerging in Canada.

“It’s been really important in the U.S. for unlocking a lot of renewable energy development,” said Sara Hastings-Simon, founding director of the Business Renewable Centre Canada, which seeks to help corporate buyers source renewable energy directly from project developers.

“You have some companies where . . . it’s what their investors and customers are demanding. I think we will see in Alberta customers who see this as a good way to meet their carbon compliance requirements.

“And the third motivation to do it is you can get the power at a good price.”

Just last month, Perimeter Solar signed an agreement with TC Energy to supply the Calgary-based firm with 74 megawatts from its solar project near Claresholm.

More deals in the industry are being discussed, and it’s expected this shift will drive other projects forward.

There is increasing interest from corporations to buy solar and wind energy directly from generators.

“The single-biggest change has been the price of wind and solar,” Arnold said in an interview.

“Alberta looks really, really bright right now because we have an open market. All other provinces, for regulatory reasons, we can’t have this (deal) . . . between a generator and a corporate buyer of power. So Alberta has a great advantage there.”

These forces are emerging as the renewable energy industry has seen dramatic change in recent years in Alberta, with costs dropping and an array of wind and solar developments moving ahead, even as solar expansion faces challenges in the province.

The former NDP government had an aggressive target to see green energy sources make up 30 per cent of all electricity generation by 2030.

Last week, the Alberta Electric System Operator put out its long-term outlook, with its base-case scenario projecting moderate demand growth for power over the next two decades. However, the expected load growth — expanding by an average of 0.9 per cent annually until 2039 — is only half the rate seen in the past 20 years.

Natural gas will become the main generation source in the province as coal-fired power (now comprising more than one-third of generation) is phased out.

Renewable projects initiated under the former NDP government’s REP program will come online in the near term, while “additional unsubsidized renewable generation is expected to develop through competitive market mechanisms and support from corporate power purchase agreements,” the report states.

AESO forecasts installed generation capacity for renewables will almost double to about 19 per cent by 2030, with wind and solar increasing to 21 per cent by 2039.

Another key policy issue for the sector will likely come within the next few weeks when the provincial government introduces details of its new Technology Innovation and Emissions Reduction program (TIER).

The initiative will require large industrial emitters to reduce greenhouse gas emissions to a benchmark level, pay into the technology fund, or buy offsets or credits. The carbon price is expected to be around $20 to $30 a tonne, and the system will kick in on Jan. 1, 2020.

Industry players point out the decision to stick with Alberta’s energy-only market along with the details surrounding TIER, and a focus by government on reducing red tape, should all help the sector attract investment.

“It is pretty clear there is a path forward for renewables here in the province,” said Evan Wilson, regional director with the Canadian Wind Energy Association.

All of these factors are propelling the wind and solar sector forward in the province, at the same time the oil and gas sector faces challenges to grow.

But it doesn’t have to be an either/or choice for the province moving forward. We’re going to need many forms of energy in the coming decades, and Alberta is an energy powerhouse, with potential to develop more wind and solar, as well as oil and natural gas resources.

“What we see sometimes is the politics and discussion around renewables or oil becomes a deliberate attempt to polarize people,” Arnold added.

“What we are trying to show, in working in Alberta on renewable projects, is it doesn’t have to be polarizing. There are a lot of solutions.

“The combination of solutions is part of what we need to talk about.”

 

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Ontario faces growing electricity supply gap, study finds

Ontario Electricity Capacity Gap threatens reliability as IESO forecasts shortfalls from the Pickering shutdown and rapid electrification, requiring new low-emission nuclear generation to meet net-zero targets, maintain baseload, and stabilize the grid.

 

Key Points

Expected 2030 shortfalls from Pickering closure and electrification, requiring new low-emission nuclear to meet net-zero.

✅ IESO projects a 3.6-9.5 GW capacity gap by 2030

✅ Pickering shutdown removes baseload, stressing reliability

✅ New low-emission nuclear needed to meet net-zero targets

 

Ontario faces an electricity supply shortage and reliability risks in the next four to eight years and will not meet net-zero objectives without building new low-emission, nuclear generation starting as soon as possible, according to a report released yesterday by the Power Workers' Union (PWU). The capacity needed to fill the expected supply gap will be equivalent to doubling the province's planned nuclear fleet in eight years.

The planned closure of the Pickering nuclear power plant in 2025 and the increase in demand from electrification of the economy are the drivers behind a capacity gap in 2030 of at least 3.6 GW which could widen to as much as 9.5 GW, Electrification Pathways for Ontario to Reduce Emissions, finds. Ontario's Independent Electricity System Operator (IESO) has since 2013 been forecasting a significant gap in the province's electricity supply due the closure of Pickering, but has been underestimating the impact of electrification, the report says.

In addition, the electrification of buildings, transport and industry sectors that will be needed to achieve goals of net-zero emissions by 2050 that being set by the federal government and civil society will see the province's electricity demand increase by at least 130% over current planning forecasts, and potentially by over 190%. Leveraging electricity, natural gas and hydrogen synergies can reduce supply needs, but 55 GW of new electricity capacity, including new large-scale nuclear plants, will still be needed by 2050 - four times Ontario's current nuclear and hydro assets - the report finds.

These findings underscore the urgent need for a paradigm shift in Ontario's electricity planning and procurement process, the authors say, adding that immediate action is needed both to mitigate the system reliability risks and enable the significant societal benefits needed to pursue net-zero objectives. Planning for procurement to replace Pickering's capacity, or to pursue life extension options, must begin as soon as possible.

"Policymakers around the world realise climate change can't be tackled without nuclear. Ontario's nuclear fleet has delivered emissions reductions for over 50 years," PWU President Jeff Parnell said. "In fact, without building new nuclear units, Ontario will miss its emission reduction targets and carbon emissions from electricity generation will rise dramatically, as explored in why Ontario's power could get dirtier today."

"This report clearly shows that Ontario cannot sustain the low-carbon status of its hydro and nuclear-based electricity system, decarbonise its economy and meet its carbon reduction targets without new nuclear or continued operation at Pickering in the near term. Most disturbing is the fact that we are already well behind and needed to start planning for this capacity yesterday," he said.

The six operating Candu reactors at Ontario Power Generation's Pickering plant have been kept in operation to provide baseload electricity during the refurbishment of units at the Darlington and Bruce plants. Currently, the company plans to shut down Pickering units 1 and 4 in 2024 and units 5 to 8 in 2025, even as Ontario moves to refurbish Pickering B to extend life.

 

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Turning thermal energy into electricity

Near-Field Thermophotovoltaics captures radiated energy across a nanoscale gap, using thin-film photovoltaic cells and indium gallium arsenide to boost power density and efficiency, enabling compact Army portable power from emitters via radiative heat transfer.

 

Key Points

A nanoscale TPV method capturing near-field photons for higher power density at lower emitter temperatures.

✅ Nanoscale gap boosts radiative transfer and usable photon flux

✅ Thin-film InGaAs cells recycle sub-band-gap photons via reflector

✅ Achieved ~5 kW/m2 power density with higher efficiency

 

With the addition of sensors and enhanced communication tools, providing lightweight, portable power has become even more challenging, with concepts such as power from falling snow illustrating how diverse new energy-harvesting approaches are. Army-funded research demonstrated a new approach to turning thermal energy into electricity that could provide compact and efficient power for Soldiers on future battlefields.

Hot objects radiate light in the form of photons into their surroundings. The emitted photons can be captured by a photovoltaic cell and converted to useful electric energy. This approach to energy conversion is called far-field thermophotovoltaics, or FF-TPVs, and has been under development for many years; however, it suffers from low power density and therefore requires high operating temperatures of the emitter.

The research, conducted at the University of Michigan and published in Nature Communications, demonstrates a new approach, where the separation between the emitter and the photovoltaic cell is reduced to the nanoscale, enabling much greater power output than what is possible with FF-TPVs for the same emitter temperature.

This approach, which enables capture of energy that is otherwise trapped in the near-field of the emitter is called near-field thermophotovoltaics or NF-TPV and uses custom-built photovoltaic cells and emitter designs ideal for near-field operating conditions, alongside emerging smart solar inverters that help manage conversion and delivery.

This technique exhibited a power density almost an order of magnitude higher than that for the best-reported near-field-TPV systems, while also operating at six-times higher efficiency, paving the way for future near-field-TPV applications, including remote microgrid deployments in extreme environments, according to Dr. Edgar Meyhofer, professor of mechanical engineering, University of Michigan.

"The Army uses large amounts of power during deployments and battlefield operations and must be carried by the Soldier or a weight constrained system," said Dr. Mike Waits, U.S. Army Combat Capabilities Development Command's Army Research Laboratory. "If successful, in the future near-field-TPVs could serve as more compact and higher efficiency power sources for Soldiers as these devices can function at lower operating temperatures than conventional TPVs."

The efficiency of a TPV device is characterized by how much of the total energy transfer between the emitter and the photovoltaic cell is used to excite the electron-hole pairs in the photovoltaic cell, where insights from near-light-speed conduction research help contextualize performance limits in semiconductors. While increasing the temperature of the emitter increases the number of photons above the band-gap of the cell, the number of sub band-gap photons that can heat up the photovoltaic cell need to be minimized.

"This was achieved by fabricating thin-film TPV cells with ultra-flat surfaces, and with a metal back reflector," said Dr. Stephen Forrest, professor of electrical and computer engineering, University of Michigan. "The photons above the band-gap of the cell are efficiently absorbed in the micron-thick semiconductor, while those below the band-gap are reflected back to the silicon emitter and recycled."

The team grew thin-film indium gallium arsenide photovoltaic cells on thick semiconductor substrates, and then peeled off the very thin semiconductor active region of the cell and transferred it to a silicon substrate, informing potential interfaces with home battery systems for distributed use.

All these innovations in device design and experimental approach resulted in a novel near-field TPV system that could complement distributed resources in virtual power plants for resilient operations.

"The team has achieved a record ~5 kW/m2 power output, which is an order of magnitude larger than systems previously reported in the literature," said Dr. Pramod Reddy, professor of mechanical engineering, University of Michigan.

Researchers also performed state-of-the-art theoretical calculations to estimate the performance of the photovoltaic cell at each temperature and gap size, informing hybrid designs with backup fuel cell solutions that extend battery life, and showed good agreement between the experiments and computational predictions.

"This current demonstration meets theoretical predictions of radiative heat transfer at the nanoscale, and directly shows the potential for developing future near-field TPV devices for Army applications in power and energy, communication and sensors," said Dr. Pani Varanasi, program manager, DEVCOM ARL that funded this work.

 

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