TVA manager: Utility a leader in cutting emissions

U.S. coal-fired generation 2021 rose as higher natural gas prices, stable coal costs, and a recovering power sector shifted the generation mix; capacity factors rebounded despite low coal stocks and ongoing plant retirements.

Key Points

Coal output rose 22% on high gas prices and higher capacity factors; a 5% decline is expected in 2022.

✅ Natural gas delivered cost averaged $4.93/MMBtu, more than double 2020

✅ Coal capacity factor rose to ~51% from 40% in 2020

✅ 2022 coal generation forecast to fall about 5%

We expect 22% more U.S. coal-fired generation in 2021 than in 2020, according to our latest Short-Term Energy Outlook (STEO). The U.S. electric power sector has been generating more electricity from coal-fired power plants this year as a result of significantly higher natural gas prices and relatively stable coal prices, even as non-fossil sources reached 40% of total generation. This year, 2021, will yield the first year-over-year increase in coal generation in the United States since 2014, highlighted by a January power generation jump earlier in the year.

Coal and natural gas have been the two largest sources of electricity generation in the United States. In many areas of the country, these two fuels compete to supply electricity based on their relative costs and sensitivity to policies and gas prices as well. U.S. natural gas prices have been more volatile than coal prices, so the cost of natural gas often determines the relative share of generation provided by natural gas and coal.

Because natural gas-fired power plants convert fuel to electricity more efficiently than coal-fired plants, record natural gas generation has at times underscored that advantage, and natural gas-fired generation can have an economic advantage even if natural gas prices are slightly higher than coal prices. Between 2015 and 2020, the cost of natural gas delivered to electric generators remained relatively low and stable. This year, however, natural gas prices have been much higher than in recent years. The year-to-date delivered cost of natural gas to U.S. power plants has averaged $4.93 per million British thermal units (Btu), more than double last year’s price.

The overall decline in electricity demand in 2020 and record-low natural gas prices led coal plants to significantly reduce the percentage of time that they generated power. In 2020, the utilization rate (known as the capacity factor) of U.S. coal-fired generators averaged 40%. Before 2010, coal capacity factors routinely averaged 70% or more. This year’s higher natural gas prices have increased the average coal capacity factor to about 51%, which is almost the 2018 average, a year when wind and solar reached 10% nationally.

Although rising natural gas prices have resulted in more U.S. coal-fired generation than last year, this increase in coal generation will most likely not continue as solar and wind expand in the generation mix. The electric power sector has retired about 30% of its generating capacity at coal plants since 2010, and no new coal-fired capacity has come online in the United States since 2013. In addition, coal stocks at U.S. power plants are relatively low, and production at operating coal mines has not been increasing as rapidly as the recent increase in coal demand. For 2022, we forecast that U.S. coal-fired generation will decline about 5% in response to continuing retirements of generating capacity at coal power plants and slightly lower natural gas prices.

Related News

• Electricity Forum News

• Power Generation News

Nuclear Power Resilience During COVID-19 shows low-carbon electricity supporting renewables integration with grid flexibility, reliability, and inertia, sustaining decarbonization, stable baseload, and system security while prices fell and demand dropped across markets.

Key Points

It shows nuclear plants providing reliable, low-carbon power and supporting grid stability despite demand declines.

✅ Low prices challenge investment; lifetime extensions are cost-effective.

✅ Nuclear provides inertia, reliability, and dispatchable capacity.

✅ Market reforms should reward flexibility and grid services.

The COVID-19 pandemic has transformed the operation of power systems across the globe, including European responses that many argue accelerated the transition, and offered a glimpse of a future electricity mix dominated by low carbon sources.

The performance of nuclear power, in particular, demonstrates how it can support the transition to a resilient, clean energy system well beyond the COVID-19 recovery phase, and its role in net-zero pathways is increasingly highlighted by analysts today.

Restrictions on economic and social activity during the COVID-19 outbreak have led to an unprecedented and sustained decline in demand for electricity in many countries, in the order of 10% or more relative to 2019 levels over a period of a few months, thereby creating challenging conditions for both electricity generators and system operators (Fig. 1). The recent Sustainable Recovery Report by the International Energy Agency (IEA) projects a 5% reduction in global electricity usage for the entire year 2020, with a record 5.7% decline foreseen in the United States alone. The sustainable economic recovery will be discussed at today's IEA Clean Energy Transitions Summit, where Fatih Birol's call to keep options open will be prominent as IAEA Director General Rafael Mariano Grossi participates.

Electricity generation from fossil fuels has been hard hit, due to relatively high operating costs compared to nuclear power and renewables, as well as simple price-setting mechanisms on electricity markets. By contrast, low-carbon electricity prevailed during these extraordinary circumstances, with the contribution of renewable electricity rising in a number of countries as analyses see renewables eclipsing coal by 2025, due to an obligation on transmission system operators to schedule and dispatch renewable electricity ahead of other generators, as well as due to favourable weather conditions.

Nuclear power generation also proved to be resilient, reliable and adaptable. The nuclear industry rapidly implemented special measures to cope with the pandemic, avoiding the need to shut down plants due to the effects of COVID-19 on the workforce or supply chains. Nuclear generators also swiftly adapted to the changed market conditions. For example, EDF Energy was able to respond to the need of the UK grid operator by curtailing sporadically the generation of its Sizewell B reactor and maintain a cost-efficient and secure electricity service for consumers.

Despite the nuclear industry's performance during the pandemic, faced with significant decreases in demand, many generators have still needed to reduce their overall output appreciably, for example in France, Sweden, Ukraine, the UK and to a lesser extent Germany (Fig. 2), even as the nuclear decline debate continues in Europe. Declining demand in France up to the end of March already contributed to a 1% drop in first quarter revenues at EDF, with nuclear output more than 9% lower than in the year before. Similarly, Russia's Rosatom experienced a significant demand contraction in April and May, contributing to an 11% decline in revenues for the first five months of the year.

Overall, the competitiveness and resilience of low carbon technologies have resulted in higher market shares for nuclear, solar and wind power in many countries since the start of lockdowns (Fig. 3), and low-emissions sources to meet demand growth over the next three years. The share of nuclear generation in South Korea rose by almost 9 percentage points during the pandemic, while in the UK, nuclear played a big part in almost eliminating coal generation for a period of two months. For the whole of 2020, the US Energy Information Administration's Short-Term Energy Outlook sees the share of nuclear generation increasing by more than one percentage point compared to 2019. In China, power production decreased during January-February 2020 by more than 8% year on year: coal power decreased by nearly 9%, hydropower by nearly 12%. Nuclear has proved more resilient with a 2% reduction only. The benefits of these higher shares of clean energy in terms of reduced emissions of greenhouse gases and other air pollutants have been on full display worldwide over the past months.

Challenges for the future

Despite the demonstrated performance of a cleaner energy system through the crisis - including the capacity of existing nuclear power plants to deliver a competitive, reliable, and low carbon electricity service when needed - both short- and long-term challenges remain.

In the shorter term, the collapse in electricity demand has accelerated recent falls in electricity prices, particularly in Europe (Fig. 4), from already economically unsustainable levels. According to Standard and Poor's Midyear Update, the large price drops in Europe result from not only COVID-19 lockdown measures but also collapsing demand due to an unusually warm winter, increased supply from renewables in a context of lower gas prices and CO2 allowances . Such low prices further exacerbate the challenging environment faced by many electricity generators, including nuclear plants. These may impede the required investments in the clean energy transition, with longer term consequences on the achievement of climate goals.

For nuclear power, maintaining and extending the operation of existing plants is essential to support and accelerate the transition to low carbon energy systems. With a supportive investment environment, a 10-20 year lifetime extension can be realized at an average cost of US $30-40/MW*h, making it among the most cost-effective low-carbon options, while also maintaining dispatchable capacity and lowering the overall cost of the clean energy transition. The IEA Sustainable Recovery report indicates that without such extensions 40% of the nuclear fleet in developed economies may be retired within a decade, adding around US$ 80 billion per year to electricity bills. The IEA note the potential for nuclear plant maintenance and extension programmes to support recovery measures by generating significant economic activity and employment.

The need for flexibility

New nuclear power projects can provide similar economic and environmental benefits and applications beyond electricity, but will be all the more challenging to finance without strong policy support and more substantive power market reforms, including improved frameworks for remunerating reliability, flexibility and other services. The need for flexibility in electricity generation and system operation - a trend accelerated by the crisis - will increasingly characterize future energy systems over the medium to longer term.

Looking further ahead, while generators and system operators successfully responded to the crisis, the observed decline in fossil fuel generation draws attention to additional grid stability challenges likely to emerge further into the energy transition. Heavy rotating steam and gas turbines provide mechanical inertia to an electricity system, thereby maintaining its balance. Replacing these capacities with variable renewables may result in greater instability, poorer power quality and increased incidence of blackouts. Large nuclear power plants along with other technologies can fill this role, alleviating the risk of supply disruptions in fully decarbonized electricity systems.

The challenges created by COVID-19 have also brought into focus the need to ensure resilience is built-in to future energy systems to cope with a broader range of external shocks, including more variable and extreme weather patterns expected from climate change.

The performance of nuclear power during the crisis provides a timely reminder of its ongoing contribution and future potential in creating a more sustainable, reliable, low carbon energy system.

Data sources for electricity demand, generation and prices: European Network of Transmission System Operators for Electricity (Europe), Ukrenergo National Power Company (Ukraine), Power System Operation Corporation (India), Korea Power Exchange (South Korea), Operador Nacional do Sistema Eletrico (Brazil), Independent Electricity System Operator (Ontario, Canada), EIA (USA). Data cover 1 January to May/June.

Related News

• Electricity Forum News

• Power Generation News

Alberta electricity price spike drives 25% CPI surge amid heatwave demand, coal-to-gas conversions, hydro shortfalls, and outages; consumers weigh fixed-rate plans, solar panels, home retrofits, and variable rates to manage bills and grid volatility.

Key Points

A recent 25% monthly rise in Alberta power prices driven by heatwave demand, constraints, outages, and fuel shifts.

✅ Heatwave pushed summer peak demand near record

✅ Coal-to-gas conversions and outages tightened supply

✅ Fixed-rate plans, solar, retrofits can reduce bill risk

Albertans might notice they are paying more when the next electricity bill comes in as bills on the rise in Calgary alongside provincial trends.

According to the consumer price index, Alberta saw its largest monthly increase since July 2015 as the price of electricity in Alberta rose 25 per cent amid rising electricity prices across the province.

“So I paid negative $70 last month. I actually made money. To supply power to the grid,” said Conrad Nobert, with Climate Action Edmonton.

Norbert is an environmental activist who favours solar power and is warning that prices will continue to go up along with the rising effects from climate change.

“My thoughts are that we can mitigate the price of power going up by taking climate action.”

Alberta experienced one of the hottest summers on record and many people were left scrambling to buy air conditioners.

That demand, along with a number of other factors, drove up prices, prompting some households to lock in rates for protection, says an assistant professor at the University of Calgary who teaches electricity systems.

“At the end of June, during the heatwave, we were a couple megawatts shy of setting an all-time record demand for electricity in the province. That would have been the first time that record for demand in the summer. Traditionally Alberta is a winter peaking province, as shown by an electricity usage record during a deep freeze not long ago,” explained Sara Hastings Simon, an assistant professor at the University of Calgary.

Other reasons for the spike: Alberta’s continuing shift from coal to natural-gas-fired power and changes to electricity production and pricing across the market.

There are a few ways consumers can save money on their power bill; installing solar panels and retrofitting your home to opting for a fixed-rate plan, or considering protections like a consumer price cap where applicable.

“So by default, people are put into a variable rate plan, that changes month to month and that helps to manage prices so you don’t get that big surprise at where prices might be. I think we will get a lot more people looking at that option.”

A statement provided by Dale Nally, Alberta’s Associate Minister of natural gas and electricity, noted recent policy changes including the carbon tax repeal and price cap now in place that affect consumers, says in part:

“This period of high market prices is driven by low supplies of hydro-generated electricity from British Columbia and the pacific northwest, scheduled outages for coal-gas-conversions, unplanned infrastructure outages and unprecedented, and record-breaking high demand due to hot weather. We expect some of the factors that have caused recent increases in prices will be short-term.”

Related News

• Electricity Forum News

• Energy Policy News

US Electricity Demand Outlook examines EIA forecasts, GDP decoupling, energy efficiency, electrification, electric vehicles, grid load growth, and weather variability to frame long term demand trends and utility planning scenarios.

Key Points

An analysis of EIA projections showing demand decoupling from GDP, with EV adoption and efficiency shaping future grid load.

✅ EIA lowers load growth; demand decouples from GDP.

✅ Efficiency and sector shifts depress kWh sales.

✅ EV adoption could revive load and capacity needs.

Electricity producers and distributors are in an unusual business. The product they provide is available to all customers instantaneously, literally at the flip of a switch. But the large amount of equipment, both hardware and software to do this takes years to design, site and install.

From a long range planning perspective, just as important as a good engineering design is an accurate sales projections. For the US electric utility industry the most authoritative electricity demand projec-tions come from the Department of Energy’s Energy Information Administration (EIA). EIA's compre-hensive reports combine econometric analysis with judgment calls on social and economic trends like the adoption rate of new technologies that could affect future electricity demand, things like LED light-ing and battery powered cars, and the rise of renewables overtaking coal in generation.

Before the Great Recession almost a decade ago, the EIA projected annual growth in US electricity production at roughly 1.5 percent per year. After the Great Recession began, the EIA lowered its projections of US electricity consumption growth to below 1 percent. Actual growth has been closer to zero. While the EIA did not antici-pate the last recession or its aftermath, we cannot fault them on that.

After the event, though, the EIA also trimmed its estimates of economic growth. For the 2015-2030 period it now predicts 2.1 percent economic and 0.3 percent electricity growth, down from previously projections of 2.7 percent and 1.3 percent respectively. (See Figures 1 and 2.)

Table 1. EIA electric generation projections by year of forecast (kWh billions)

Table 2. EIA forecast of GDP by year of forecast (billion 2009 $)

Back in 2007, the EIA figured that every one percent increase in economic activity required a 0.48 percent in-crease in electric generation to support it. By 2017, the EIA calculated that a 1 percent growth in economic activity now only required a 0.14 percent increase in electric output. What accounts for such a downgrade or disconnect between electricity usage and economic growth? And what factors might turn the numbers 
around?

First, the US economy lost energy intensive heavy industry like smelting, steel mills and refineries; patterns in China's electricity sector highlight how industrial shifts can reshape power demand. A more service oriented economy (think health care) relies more heavily on the movement of data or information and uses far less power than a manufacturing-oriented economy.

A small volcano in Argentina is about to fuel the next tech boom – and a little known company is going to be right at the center. Early investors stand to gain incredible profits and you can too. Read the report.

Second, internet shopping has hurt so-called "brick and mortar" retailers. Despite the departure of heavy industry, in years past a burgeoning US commercial sector increased its demand and usage of electricity to offset the industrial decline. But not anymore. Energy efficiency measures as well as per-haps greater concern about global warming and greenhouse gas emissions and have cut into electricity sales. “Do more with less” has the right ring to it.

But there may be other components to the ongoing decline in electricity usage. Academic studies show that electricity usage seems to increase with income along an S curve, and flattens out after a certain income level. That is, if you earn $1 billion per year you do not (or cannot) use ten times a much electricity as someone earning only $100 million.

But people at typical, middle income levels increase or decrease electricity usage when incomes rise or fall. The squeeze on middle income families was discussed often in the late presidential campaign. In recent decades an increasing percentage of income has gone to a small percentage of the population at the top of the income scale. This trend probably accounts for some weakness in residential sales. This suggests that government policy addressing income inequality would also boost electricity sales.

Population growth affects demand for electricity as well as the economy as a whole. The EIA has made few changes in its projections, showing 0.7 percent per year population growth in 2015- 2030 in both the 2007 and 2017 forecasts. Recent studies, however, have shown a drop in the birth rate to record lows. More troubling, from a national health perspective is that the average age of death may have stopped rising. Those two factors point to lower population growth, especially if the government also restricts immi-gration. Thus, the US may be approaching a period of rather modest population growth.

All of the above factors point to minimal sales growth for electricity producers in the US--perhaps even lower than the seemingly conservative EIA estimates. But the cloud on the horizon has a silver lining in the shape of an electric car. Both the United Kingdom and France have set dates to end of production of automobiles with internal combustion engines. Several European car makers have declared that 20 percent of their output will be electric vehicles by the early 2020s. If we adopt automobiles powered by electricity and not gasoline or diesel, electricity sales would increase by one third. For the power indus-try, electric vehicles represent the next big thing.

We don’t pretend to know how electric car sales will progress. But assume vehicle turnover rates re-main at the current 7 percent per year and electric cars account for 5 percent of sales in the first five years (as op-posed to 1 percent now), 20 percent in the next five years and 50 percent in the third five year period. Wildly optimistic assumptions? Maybe. By 2030, electric cars would constitute 28 percent of the vehicle fleet. They would add about 10 percent to kilowatt hour sales by that date, assuming that battery efficiencies do not improved by then. Those added sales would require increased electric generation output, with low-emissions sources expected to cover almost all the growth globally. They would also raise long term growth rates for 2015-2030 from the present 0.3 percent to 1.0 percent. The slow upturn in demand should give the electric companies time to gear up so to speak.

In the meantime, weather will continue to play a big role in electricity consumption. Record heat-induced demand peaks are being set here in the US even as surging global demand puts power systems under strain worldwide.

Can we discern a pattern in weather conditions 15 years out? Maybe we can, but that is one topic we don’t expect a government agency to tackle in public right now. Meantime, weather will affect sales more than anything else and we cannot predict the weather. Or can we?

Related News

• Electricity Forum News

• Power Generation News

Texas Electric Cooperatives outperformed during Winter Storm Uri, with higher customer satisfaction, equitable rolling blackouts, and stronger grid reliability compared to deregulated markets, according to ERCOT-area survey data of regulated utilities and commercial providers.

Key Points

Member-owned utilities in Texas delivering power, noted for reliability and fair outages during Winter Storm Uri.

✅ Member-owned, regulated utilities serving local communities

✅ Rated higher for blackout management and communication

✅ Operate outside deregulated markets; align incentives with users

Winter Storm Uri began to hit parts of Texas on February 13, 2021 and its onslaught left close to 4.5 million Texas homes and businesses without power, and many faced power and water disruptions at its peak. By some accounts, the preliminary number of deaths attributed to the storm is nearly 200, and the economic toll for the Lone Star State is estimated to be as high as $295 billion. 

The more than two-thirds of Texans who lost power during this devastating storm were notably more negative than positive in their evaluation of the performance of their local electric utility, mirrored by a rise in electricity complaints statewide, with one exception. That exception are the members of the more than 60 electric cooperatives operating within the Texas Interconnection electrical grid, which, in sharp contrast to the customers of the commercial utilities that provide power to the majority of Texans, gave their local utility a positive evaluation related to its performance during the storm.

In order to study Winter Storm Uri’s impact on Texas, the Hobby School of Public Affairs at the University of Houston conducted an online survey during the first half of March of residents 18 and older who live in the 213 counties (91.5% of the state population) served by the Texas power grid, which is managed by the Electric Reliability Council of Texas (ERCOT). 

Three-quarters of the survey population (75%) live in areas with a deregulated utility market, where a specified transmission and delivery utility by region is responsible for delivering the electricity (purchased from one of a myriad of private companies by the consumer) to homes and businesses. The four main utility providers are Oncor, CenterPoint CNP -2.2%, American Electric Power (AEP) North, and American Electric Power (AEP) Central. 

The other 25% of the survey population live in areas with regulated markets, where a single company is responsible for both delivering the electricity to homes and businesses and serves as the only source from which electricity is purchased. Municipal-owned and operated utilities (e.g., Austin Energy, Bryan Texas Utilities, Burnet Electric Department, Denton Municipal Electric, New Braunfels Utilities, San Antonio’s CPS Energy CMS -2.1%) serve 73% of the regulated market. Electric cooperatives (e.g., Bluebonnet Electric Cooperative, Central Texas Electric Cooperative, Guadalupe Valley Cooperative, Lamb County Electric Cooperative, Pedernales Electricity Cooperative, Wood County Electric Cooperative) serve one-fifth of this market (21%), with private companies accounting for 6% of the regulated market.

The overall distribution of the survey population by electric utility providers is: Oncor (38%), CenterPoint (21%), municipal-owned utilities (18%), AEP Central & AEP North combined (12%), electric cooperatives (6%), other providers in the deregulated market (4%) and other providers in the regulated market (1%). 

There were no noteworthy differences among the 31% of Texans who did not lose power during the winter storm in regard to their evaluations of their local electricity provider or their belief that the power cuts in their locale were carried out in an equitable manner.  

However, among the 69% of Texans who lost power, those served by electric cooperatives in the regulated market and those served by private electric utilities in the deregulated market differed notably regarding their evaluation of the performance of their local electric utility, both in regard to their management of the rolling blackouts, amid debates over market reforms to avoid blackouts, and to their overall performance during the winter storm. Those Texans who lost power and are served by electric cooperatives in a regulated market had a significantly more positive evaluation of the performance of their local electric utility than did those Texans who lost power and are served by a private company in a deregulated electricity market. 

For example, only 24% of Texans served by electric cooperatives had a negative evaluation of their local electric utility’s overall performance during the winter storm, compared to 55%, 56% and 61% of those served by AEP, Oncor and CenterPoint respectively. A slightly smaller proportion of Texans served by electric cooperatives (22%) had a negative evaluation of their local electric utility’s performance managing the rolling blackouts during the winter storm, compared to 58%, 61% and 71% of Texans served by Oncor, AEP and CenterPoint, respectively.

Texans served by electric cooperatives in regulated markets were more likely to agree that the power cuts in their local area were carried out in an equitable manner compared to Texans served by commercial electricity utilities in deregulated markets. More than half (52%) of those served by an electric cooperative agreed that power cuts during the winter storm in their area were carried out in an equitable manner, compared to only 26%, 23% and 23% of those served by Oncor, AEP and CenterPoint respectively

The survey data did not allow us to provide a conclusive explanation as to why the performance during the winter storm by electric cooperatives (and to a much lesser extent municipal utilities) in the regulated markets was viewed more favorably by their customers than was the performance of the private companies in the deregulated markets viewed by their customers. Yet here are three, far from exhaustive, possible explanations.

First, electric cooperatives might have performed better (based on objective empirical metrics) during the winter storm, perhaps because they are more committed to their customers, who are effectively their bosses. .  

Second, members of electric cooperatives may believe their electric utility prioritizes their interests more than do customers of commercial electric utilities and therefore, even if equal empirical performance were the case, are more likely to rate their electric utility in a positive manner than are customers of commercial utilities.  

Third, regulated electric utilities where a single entity is responsible for the commercialization, transmission and distribution of electricity might be better able to respond to the type of challenges presented by the February 2021 winter storm than are deregulated electric utilities where one entity is responsible for commercialization and another is responsible for transmission and distribution, aligning with calls to improve electricity reliability across Texas.

Other explanations for these findings may exist, which in addition to the three posited above, await future empirical verification via new and more comprehensive studies designed specifically to study electric cooperatives, large commercial utilities, and the incentives that these entities face under the regulatory system governing production, commercialization and distribution of electricity, including rulings that some plants are exempt from providing electricity in emergencies under state law. 

Still, opinion about electricity providers during Winter Storm Uri is clear: Texans served by regulated electricity markets, especially by electric cooperatives, were much more satisfied with their providers’ performance than were those in deregulated markets. Throughout its history, Texas has staunchly supported the free market. Could Winter Storm Uri change this propensity, or will attempts to regulate electricity lessen as the memories of the storm’s havoc fades? With a hotter summer predicted to be on the horizon in 2021 and growing awareness of severe heat blackout risks, we may soon get an answer.   

Related News

• Electricity Forum News

• Energy Policy News

Raindrop Triboelectric Energy Harvesting converts falling water into electricity using Teflon (PTFE) on indium tin oxide and an aluminum electrode, forming a transient water bridge; a low frequency nanogenerator for renewable, static electricity harvesting.

Key Points

A method using PTFE, ITO, and an aluminum electrode to turn raindrop impacts into low frequency electrical power.

✅ PTFE on ITO boosts charge transfer efficiency.

✅ Water bridge links electrodes for rapid discharge.

✅ Low frequency output suits continuous energy harvesting.

Scientists at the City University of Hong Kong have used a Teflon-coated surface and a phenomenon called triboelectricity to generate a charge from raindrops. “Here we develop a device to harvest energy from impinging water droplets by using an architecture that comprises a polytetrafluoroethylene [Teflon] film on an indium tin oxide substrate plus an aluminium electrode,” they explain in their new paper in Nature as a step toward cheap, abundant electricity in the long term.

Triboelectricity itself is an old concept. The word means “friction electricity”—from the Greek tribo, to rub or wear down, which is why a diatribe tires you out—and dates back a long, long time. Static electricity is the most famous kind of triboelectric, and related work has shown electricity from the night sky can be harvested as well in niche setups. In most naturally occurring kinds, scientists have studied triboelectric in order to avoid its effects, like explosions inside of grain silos or hospital workers touching off pure oxygen. (Blowing sand causes an electric field, and NASA even worries about static when astronauts eventually land on Mars.)

One of the most studied forms of intentional and useful triboelectric is in systems such as ocean wave generators where the natural friction of waves meets nanogenerators of triboelectric energy. These even already use Teflon, which has natural conductivity that makes it ideal for this job. But triboelectricity is chaotic, and harnessing it generally involves a bunch of complicated, intersecting variables that can vary with the hourly weather. Promises of static electricity charging devices have often been, well, so much hot, sandy wind.

The scientists at City University of Hong Kong used triboelectric ideas to turn falling raindrops into energy. They say previous versions of the same idea were not very efficient, with materials that didn’t allow for high-fidelity transfer of electrical charge. (Many sources of renewable energy aren’t yet as efficient to turn into power, both because of developing technology and because their renewability means even less efficient use could be better than, for example, fossil fuels, and advances in renewable energy storage could help.)

“[A]chieving a high density of electrical power generation is challenging,” the team explains in its paper. “Traditional hydraulic power generation mainly uses electromagnetic generators that are heavy, bulky, and become inefficient with low water supply.” Diversifying how power is generated by water sources such as oceans and rivers is good for the existing infrastructure as well as new installations.

The research team found that as simulated raindrops fell on their device, the way the water accumulated and spread created a link between their two electrodes, one Teflon-coated and the other aluminum. This watery de facto wire link closes the loop and allows accumulated energy to move through the system. Because it’s a mechanical setup, it’s not limited to salty seawater, and because the medium is already water, its potential isn’t affected by ambient humidity either.

Raindrop energy is very low frequency, which means this tech joins many other existing pushes to harvest continuously available, low frequency natural energy, including underwater 'kites' that exploit steady currents. To make an interface that increases “instantaneous power density by several orders of magnitude over equivalent devices,” as the researchers say they’ve done here, could represent a major step toward feasibility in triboelectric generation.

Related News

• Electricity Forum News

• Renewable Energy News