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Electrical energy storage

Electrical Energy Storage (EES) is the process of converting electrical energy from a power network into a form that can be stored for converting back to electricity when needed. EES enables electricity to be produced during times of either low demand, low generation cost, or during periods of peak renewable energy generation. This allows producers and transmission system operators (TSOs) the ability to leverage and balance the variance in supply/demand and generation costs by using stored electricity at times of high demand, high generation cost, and/or low generation capacity.
EES has many applications including renewables integration, ancillary services, and electrical grid support. This blog series aims to provide the reader with four aspects of EES:

  1. An overview of the function and applications of EES technologies,
  2. State-of-the-art breakdown of key EES markets in the European Union,
  3. A discussion on the future of these EES markets, and
  4. Applications (Service Uses) of EES.

Table: Some common service uses of EES technologies

Storage Category

Storage Technology

Pumped Hydro

Open Loop

Closed Loop

Electro-chemical

Batteries

Flow Batteries

Capacitors

Thermal Storage

 

Molten Salts

Heat

Ice

Chilled Water

Electro-mechanical

Compressed Air Energy Storage

Flywheel

Gravitational Storage

Hydrogen Storage

 

Fuel Cells

H2 Storage

Power-to-Gas

Unlike any other commodities market, electricity-generating industries typically have little or no storage capabilities. Electricity must be used precisely when it is produced, with grid operators constantly balancing electrical supply and demand. With an ever-increasing market share of intermittent renewable energy sources the balancing act is becoming increasingly complex.

While EES is most often touted for its ability to help minimize supply fluctuations by storing electricity produced during periods of peak renewable energy generation, there are many other applications. EES is vital to the safe, reliable operation of the electricity grid by supporting key ancillary services and electrical grid reliability functions. This is often overlooked for the ability to help facilitate renewable energy integration. EES is applicable in all of the major areas of the electricity grid (generation, transmission & distribution, and end user services). A few of the most prevalent service uses are outlined in the Table above. Further explanation on service use/cases will be provide later in this blog, including comprehensive list of EES applications.

Area

Service
Use/Case

Discharge
Duration in h

Capacity
in MW

Examples

Generation

Bulk
Storage

4
– 6

1
– 500

PHS,
CAES, Batteries

Contingency

1
– 2

1
– 500

PHS,
CAES, Batteries

Black
Start

NA

NA

Batteries

Renewables
Firming

2
– 4

1
– 500

PHS,
CAES, Batteries

Transmission
& Distribution

Frequency
& Voltage Support

0.25
– 1

1
– 10

Flywheels,
Capacitors

Transmission
Support

2
– 5 sec

10
– 100

Flywheels,
Capacitors

On-site
Power

8
– 16

1.5
kW – 5 kW

Batteries

Asset
Deferral

3
– 6

0.25
– 5

Batteries

End
User Services

Energy
Management

4
– 6

1
kW – 1 MW

Residential
storage

(Jon Martin, 2019)

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EU market summary for energy storage

Electrical energy storage (EES) is not only a vital component in the reliable operation of modern electrical grids, but also a focal point of the global renewable energy transition. It has been often suggested that EES technologies could be the missing piece to eliminating the technical hurdles facing the implementation of intermittent renewable energy sources. In the following blog posts, selected EES markets within the European Union will be evaluated in detail.

With over 80 MW of installed wind and solar capacity, Germany is by far the leading EU nation in the renewable energy transition. However, experts have argued that Germany’s need for widespread industrial scale energy storage is unlikely to materialize in any significant quantity for up to 20-years. This is due to a number of factors. Germany’s geographic location and abundance of connections to neighbouring power grids makes exporting any electricity fluctuations relatively easy. Additionally, when Germany reaches its 2020 targets for wind and solar capacity (46 GW and 52 GW, respectively) the supply at a given time would generally not exceed 55 GW. Nearly all of this would be consumed domestically, with no/little need for storage.

When evaluating energy storage in the UK, a different story emerges. Being an isolated island nation there is considerably more focus on energy independence to go along with their low-carbon energy goals. However, the existing regulatory environment is cumbersome, and poses barriers significant enough to substantially inhibit the transition to a low-carbon energy sector – including EES. The UK government has acknowledged the existence of regulatory barriers and pledged to address them. As part of this effort, a restructuring of their power market to a capacity-based market is already underway. The outlook for EES in the UK is promising, there is considerable pressure from not only industry, but also the public and the government to continue developing EES facilities at industrial scale.

Italy, once heavily hydro-powered, has grown to rely on natural gas, coal, and oil for 50% of it’s electricity (gas representing 34% alone). The introduction of a solar FIT in 2005 lead to significant growth in the solar industry (Italy now ranks 2nd in per capita solar capacity globally) before the program ended in July 2014. In recent years there has been notable growth in electro-chemical EES capacity (~84 MW installed), primarily driven by a single large-scale project by TERNA, Italy’s transmission system operator (TSO). This capacity has made Italy the leader in EES capacity in the EU, however the market is to-date dominated by the large TSOs.

However, the combination of a reliance on imported natural gas, over 500,000 PV systems no longer collecting FIT premiums, and increasing electricity rates presents a unique market opportunity for residential power-to-gas in Italy.
Denmark is aggressively pursing a 100-percent renewable target for all sectors by 2050. While there is still no official roadmap policy on how they will get there, they have essentially narrowed it down to one of two scenario: a biomass-based scenario, or a wind + hydrogen based scenario. Under the hydrogen-based scenario there would be widespread investment to expand wind capacity and couple this capacity with hydrogen power-to-gas systems for bulk energy storage. With the Danish expertise and embodied investment in wind energy, one would expect that the future Danish energy system would be build around this strength, and hence require significant power-to-gas investment.

The renewable energy industry in Spain has completed stagnated due to retroactive policy changes and taxes on consumption of solar generated electricity introduced in 2015. The implementation of the Royal Decree 900/2015 on self-consumption has rendered PV systems unprofitable, and added additional fees and taxes for the use of EES devices. No evidence was found to suggest a market for energy storage will materialize in Spain in the near future.

The final country investigated was the Netherlands, which has been criticized by the EU for its lack of progress on renewable energy targets. With only 10% of Dutch electricity coming from renewable sources, there is currently little demand for large-scale EES. While the Netherlands may be lagging behind on renewable electricity targets, they have been a leader in EV penetration; a trend that will continue and see 1-million EVs on Dutch roads by 2025. In parallel with the EV growth, there has been a large surge in sub-100kW Li-ion installations for storing energy at electric vehicle (EV) charging stations. It is expected that these applications will continue to be the primary focus of EES in the Netherlands.

Similar to Italy, the Dutch rely heavily on natural gas for energy within their homes. This fact, coupled with an ever-increasing focus on energy independent and efficient houses could make the Netherlands a prime market for residential power-to-gas technologies.

Read more about electrical energy storage here.

Jon Martin, 2019

(Photo: NASA)

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Producing liquid bio-electrically engineered fuels from CO2

At Frontis Energy we have spent much thought on how to recycle CO2. While high value products such as polymers for medical applications are more profitable, customer demand for such products is too low to recycle CO2 in volumes required to decarbonize our atmosphere to pre-industrial levels. Biofuel, for example from field crops or algae has long been thought to be the solution. Unfortunately, they require too much arable land. On top of their land use, biochemical pathways are too complex to understand by the human brain. Therefore, we propose a different way to quickly reach the target of decarbonizing our planet. The proce­dure begins with a desired target fuel and suggests a mi­crobial consortium to produce this fuel. In a second step, the consortium will be examined in a bio-electrical system (BES).

CO2 can be used for liquid fuel production via multiple pathways. The end product, long-chain alcohols, can be used either directly as fuel or reduced to hydrocarbons. Shown are examples of high level BEEF pathways using CO2 and electricity as input and methane, acetate, or butanol as output. Subsequent processes are 1, aerobic methane oxida­tion, 2, direct use of methane, 3 heterotrophic phototrophs, 4, acetone-butanol fermentation, 5, heterotrophs, 6, butanol di­rect use, 7, further processing by yeasts

Today’s atmospheric CO2 imbalance is a consequence of fossil carbon combus­tion. This real­ity requires quick and pragmatic solutions if further CO2 accu­mulation is to be prevented. Direct air capture of CO2 is moving closer to economic feasibility, avoid­ing the use of arable land to grow fuel crops. Producing combustible fuel from CO2 is the most promis­ing inter­mediate solution because such fuel integrates seamlessly into existing ur­ban in­frastructure. Biofuels have been ex­plored inten­sively in re­cent years, in particular within the emerging field of syn­thetic biol­ogy. How­ever tempt­ing the application of genetically modified or­ganisms (GMOs) ap­pears, non-GMO technology is easier and faster to im­plement as the re­quired microbial strains al­ready exist. Avoiding GMOs, CO2 can be used in BES to produce C1 fu­els like methane and precursors like formic acid or syngas, as well as C1+ com­pounds like ac­etate, 2-oxybut­yrate, bu­tyrate, ethanol, and butanol. At the same time, BES inte­grate well into urban in­frastructure without the need for arable land. However, except for meth­ane, none of these fuels are readily com­bustible in their pure form. While elec­tromethane is a com­mercially avail­able al­ternative to fossil natu­ral gas, its volumetric energy den­sity of 40-80 MJ/m3 is lower than that of gasoline with 35-45 GJ/m3. This, the necessary technical modifications, and the psychological barrier of tanking a gaseous fuel make methane hard to sell to automobilists. To pro­duce liq­uid fuel, carbon chains need to be elongated with al­cohols or better, hy­drocarbons as fi­nal prod­ucts. To this end, syngas (CO + H2) is theoreti­cally a viable option in the Fischer-Tropsch process. In reality, syngas pre­cursors are ei­ther fossil fu­els (e.g. coal, natural gas, methanol) or biomass. While the for­mer is ob­viously not CO2-neu­tral, the latter com­petes for arable land. The di­rect con­version of CO2 and electrolytic H2 to C1+ fuels, in turn, is catalyzed out by elec­troactive microbes in the dark (see title figure), avoid­ing food crop com­petition for sun-lit land. Unfortunately, little re­search has been under­taken beyond proof of con­cept of few electroactive strains. In stark con­trast, a plethora of metabolic studies in non-BES is avail­able. These studies often pro­pose the use of GMOs or complex or­ganic sub­strates as precur­sors. We propose to systemati­cally identify metabolic strategies for liquid bio-electrically engineered fuel (BEEF) production. The fastest approach should start by screening meta­bolic data­bases using es­tablished methods of metabolic modeling, fol­lowed by high throughput hypothesis testing in BES. Since H2 is the intermediate in bio-electrosynthesis, the most efficient strategy is to focus on CO2 and H2 as di­rect pre­cursors with as few in­termediate steps as pos­sible. Scala­bility and energy effi­ciency, eco­nomic feasibil­ity that is, are pivotal elements.

First, an electrotrophic acetogen produces acetate, which then used by heterotrophic algae in a consecutive step.

The biggest obstacle for BEEF production is lacking knowledge about pathways that use CO2 and electrolytic H2. This gap exists despite metabolic data­bases like KEGG and more recently KBase, making metabolic design and adequate BEEF strain selection a guessing game rather than an educated ap­proach. Nonetheless, metabolic tools were used to model fuel pro­duction in single cell yeasts and various prokaryotes. In spite of their shortcomings, metabolic data­bases were also employed to model species interactions, for example in a photo-het­erotroph consor­tium using software like ModelSEED / KBase (http://mod­elseed.org/), RAVEN / KEGG and COBRA. A first sys­tematic at­tempt for BEEF cul­tures produci­ng acetate demonstrated the usability of KBase for BES. This research was a bottom-up study which mapped ex­isting genomes onto existing BEEF consor­tia. The same tool can also be em­ployed in a top-down ap­proach, starting with the desired fuel to find the re­quired or­ganisms. Some possi­ble BEEF organisms are the following.

Possible pathways for BEEF production involving Clostridium, 3, or heterotrophic phototrophs, 7, further processing by yeasts

Yeasts are among the microorganisms with the greatest potential for liquid biofuel production. Baker’s yeast, (Saccha­romyces cerevisiae) is the most promi­nent exam­ple. While known for ethanol fermentat­ion, yeasts also produce fusel oils such as bu­tane, phenyl, and amyl derivate aldehy­des and alco­hols. Unlike ethanol, which is formed via sugar fer­mentation, fusel oil is syn­thesized in branched-off amino acid pathways followed by alde­hyde reduction. Many en­zymes involved in the re­duction of aldehydes have been identified, with al­cohol dehydro­genases be­ing the most commonly ob­served. The corre­sponding reduc­tion reactions require reduced NADH⁠ but it is not known whether H2 pro­duced on cathodes of BES can be in­volved.
Clostridia, for example Clostridium acetobutylicum and C. carboxidivo­rans, can pro­duce alcohols like butanol, isopropanol, hexanol, and ketones like acetone from complex sub­strates (starch, whey, cel­lulose, etc. ) or from syngas. Clostridial me­tabolism has been clarified some time ago and is dif­ferent from yeast. It does not necessar­ily require com­plex precursors for NAD+ reduction and it was shown that H2, CO, and cath­odes can donate elec­trons for alcohol production. CO2 and H2 were used in a GMO clostridium to produce high titers of isobu­tanol. Typi­cal representa­tives for acetate produc­tion from CO2 and H2 are C. ljungdahlii, C. aceticum, and Butyribac­terium methy­lotrophicum. Sporo­musa sphaeroides pro­duces acetate in BES. Clostridia also dominated mixed cul­ture BESs converting CO2 to butyrate. They are therefore prime targets for low cost biofuel production. Alcohols in clostridia are produced from acetyl-CoA. This reaction is re­versible, al­lowing ac­etate to serve as substrate for biofuel production with extra­cellular en­ergy sup­ply. Then, en­ergy con­servation, ATP syn­thesis that is, can be achieved from ethanol electron bifurca­tion or H2 oxida­tion via respi­ration. While pos­sible in anaero­bic clostridia, it is hitherto unknown whether elec­tron bifurca­tion or res­piration are linked to alcohols or ke­tone synthesis.
Phototrophs like Botryococcus produce C1+ biofuels as well. They synthesize a number of different hydro­carbons including high value alkanes and alkenes as well as terpenes. However, high titers were achieved by only means of ge­netic engineering, which is economically not feasible in many countries due to regulatory constrains. Moreover, aldehyde dehy­dration/deformylation to alkanes or alkenes requires molecular oxygen to be present. Also the olefin path­way of Syne­chococcus depends on molecular oxygen with the cytochrome P450 involved in fatty acid de­carboxylation. The presence of molecular oxygen affects BES performance due to immediate product degrada­tion and unwanted cathodic oxygen reduction. In contrast, our own preliminary experi­ments (see title photo) and a corrosion experi­ment show that algae can live in the dark using electrons from a cath­ode. While the en­zymes in­volved in the production of some algal biofuels are known (such as olefin and alde­hyde de­formylation), it is not known whether these pathways are connected to H2 utilization (perhaps via ferredox­ins). Such a con­nection would be a promising indicator for the possibility of growing hydrocar­bon produc­ing cyanobacteria on cathodes of BES and should be examined in future research.
At Frontis Energy we believe that a number of other microorganisms show potential for BEEF production and these deserve further investi­gation. To avoid GMOs, BES compatible co-cultures must be identified via in silico meta­bolic reconstruc­tion from existing databases. Possible inter-species intermediates are unknown but are prerequisite for suc­cessful BES operation. Finally, a techno-economical assessment of BEEF pro­duction, with and with­out car­bon taxes, and compared with chemical methods, will direct future research.

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Fresh CO2 − Now Even Cheaper!

Hurry up while stocks last, you may want to add. Carbon dioxide (CO2) is a waste product from the combustion of fossil fuels such as oil, gas and coal. It is almost worthless because it finds little use. However, technologies such as power-to-gas or electrosynthesis of methanol are able to convert CO2 directly into a valuable, albeit cheap, product. This increases the commercial interest in CO2 and ultimately the filtering from the air becomes economically interesting. That is, filtering CO2 from the air is now more than just an expensive strategy to fight global warming. Recently, a detailed economic analysis has been published in the journal Joule, which suggests that this filter technology could soon become a viable reality.

The study was published by the engineers of the Canadian company Carbon Engineering in Calgary, Canada. Since 2015, the company has been operating a pilot plant for CO2 extraction in British Columbia. This plant − based on a concept called Direct Air Capture (DAC) − formed the foundation for the presented economic analysis. It includes the costs from suppliers of all major components. According to the study, the cost of extracting a ton of CO2 from the air ranges from $94 to $232, depending on a variety of design options. The latest comprehensive analysis of DAC estimated $600 per tonne and was published by the American Physical Society in 2011.

In addition to Carbon Engineering, the Swiss company Climeworks also works on DAC in Zurich. There, the company has launched a commercial pilot that can absorb 900 tonnes of CO2 from the atmosphere every year for use in greenhouses. Climeworks has also opened a second plant in Iceland that can capture 50 tonnes of CO2 per year and bury it in subterranean basalt formations. According to Daniel Egger of Climeworks, capturing a ton of CO2 at their Swiss site costs about $600. He expect the number to fall below $100 per ton over the next five to ten years.

Technically, CO2 is dissolved in an alkaline solution of potassium hydroxide which reacts with CO2 to form potassium carbonate. After further processing, this becomes a solid residue of calcium carbonate, which releases the CO2 when heated. The CO2 could then be disposed of underground or used to make synthetic, CO2-neutral fuels. To accomplish this, Carbon Engineering has reduced the cost of its filtration plant to $94 per ton of CO2.

CO2-neutral fuel, from carbon dioxide captured from the air and electrolytic hydrogen.

Assuming, however, that CO2 is sequestered in rock, a price of $100 per ton would translate into 0.2 cent per liter gasoline. Ultimately, the economics of CO2 extraction depend on factors that vary by location, including the price of energy and whether or not a company can access government subsidies or a carbon trading market. But the cost per ton of DAC-CO2 is likely to remain above the real market price of CO2 in the near future. For example, emission certificates in the European Union’s trading system are around €16 per tonne of CO2. If CO2 extraction technology were to gain a foothold in markets where carbon can be sold at DAC price, then DAC would of course become economical. Conversion into useful products product such as plastic or fuel could help to include the DAC premium. Alberta seems a great location because its oil is of low quality and comes at high production costs. Moreover, the size of the DAC plant suggests this is done best in Canada, given the size of the country. Albertans may want to reconsider their business model.

At Frontis Energy, we are excited about this prospect. CO2 is accessible everywhere and DAC is helping us convert it into methane gas. Power-to-gas is perfect for this. However, there would still have something to happen. $100 per ton is already good (compared to $600), but to be able to economically place a product like methane on the market it should be more like $10 per tonne:

CO2 economy of power-to-gas with electrolytic hydrogen. Cal, California, EOR, enhanced oil recovery.

Sure, we always complain, but we still cannot wait to see how the price of DAC continues to fall and wish Carbon Engineering to Climeworks all the best. Keep it up!

(Photos: Carbon Engineering)

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You Can Have the Pie and Eat It

In Paris, humanity has set itself the goal of limiting global warming to 1.5 °C. Most people believe that this will be accompanied by significant sacrifice of quality of life. That is one reason why climate protection is simply rejected by many people, even to the point of outright denial. At Frontis Energy, we think we can protect the climate and live better. The latest study published in Nature Energy by a research group around Arnulf Grubler of the International Institute for Applied Systems Analysis in Laxenburg, Austria, has now shown that we have good reasons.

The team used computer models to explore the potential of technological trends to reduce energy consumption. Among other things, the researchers said that the use of shared car services will increase and that fossil fuels will give way to solar energy and other forms of renewable energy. Their results show that global energy consumption would decrease by about 40% regardless of population, income, and economic growth. Air pollution and demand for biofuels would also decrease, which would improve health and food supplies.

In contrast to many previous assessments, the group’s findings suggest that humans can limit the temperature rise to 1.5 °C above preindustrial levels without resorting to drastic strategies to extract CO2 from the atmosphere later in the century.

Now, one can argue whether shared car services do not cut quality of life. Nevertheless, we think that individual mobility can be maintained while protecting our climate. CO2 recovery for the production of fuels (CO2 recycling that is) is such a possibility. The Power-to-Gas technology is the most advanced version of CO2 recycling and should certainly be considered in future studies. An example of such an assessment of the power-to-gas technology was published by a Swiss research group headed by Frédéric Meylan, who found that the carbon footprint can be neutralized with conventional technology after just a few cycles.

(Picture: Pieter Bruegel the Elder, The Land of Cockaigne, Wikipedia)

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Starting up Power-to-Gas Reactors

In their paper “Effect of Start-Up Strategies and Electrode Materials on Carbon Dioxide Reduction on Biocathodes“, which was recently published in Applied and Environmental Microbiology, Saheb-Alam et al. teach us how to start-up bio-electrical systems for CO2 conversion to methane gas. They compared pre-acclimated with pristine electrodes and found that there is no difference in start-up time. Their findings stand in contrast to previous observations where pre-acclimation has indeed helped to improve reactor performance. For example, LaBarge et al. found that electrodes acclimated with methane-forming microbes, called Methanobacterium, do reduce start-up time.