Tag: natural gas

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Solid oxide fuel cells convert methane gas recovered from groundwater

Solid oxide fuel cells (SOFCs) are highly efficient energy conversion devices and have low operating costs. They work at a temperature range of 800 to 1,000 degrees Celsius. This allows for the possibility of using internal conversion of hydrocarbon fuels into hydrogen. Methane, methanol, petroleum, and other hydrocarbons can be converted to hydrogen (H2) directly within the fuel cell.

SOFCs have a number of additional advantages over traditional combustion engines or other types of fuel cells. For example, the high exhaust heat (over 800 degrees Celsius) makes them a useful application in the industry for cogeneration of electricity and heat. Because of combined cycles, high efficiency for electricity production can be achieved. In addition, due to the modular nature of SOFCs, they offer flexible planning of power generation capacity. This way, the use of SOFCs results in a further reduction of carbon dioxide emission.

The greatest advantage of SOFCs is that they can be operated with hydrocarbon fuels such as methane (CH4, the main component of natural gas). The direct use of methane eliminates the need for pre-reformers, thus reducing the complexity, size, and cost of the overall SOFC system.

Methane can be recovered from the decay of organic waste in municipal solid waste landfills, drinking water treatment plants, etc. The gas can also be recovered from groundwater because of the naturally occurring anaerobic degradation of organic matter in the subsurface or the infiltration of methane from natural gas reservoirs.

A research team from the Delft University of Technology assumed that the gas collected from groundwater treatment can be effectively used as fuel in SOFCs and put their hypothesis to a test. They published their results in the journal Journal of Cleaner Production. Currently, the methane recovered from the Drinking Water Treatment Plant (DWTP) of Spannenburg, Netherlands is either released into the atmosphere or flared, wasting a precious resource and contributing to further greenhouse emission in the form of CO2.

SOFCs provide the cleanest of the viable solutions of converting recovered methane into electrical energy, which, in turn, can be utilized by the DWTP. This process will decrease the power demands and simultaneously reduce the greenhouse gas emissions of the DWTP.

The entire process was divided into the following steps:

  1. Methane was recovered from groundwater: The groundwater was pumped from the deep-wells directly to a system of vacuum towers, which remove 90% of the dissolved gas using a near vacuum of 0.2 bar.
  2. Subsequent treatment by plate aeration was done to remove the remaining 10% of methane in the groundwater.
  3. Tower aeration used to further remove CO2 before pellet softening process to lower hardness.

Recovered gas sampling:

200 mL of the recovered gas enriched in methane was used to determine the concentration of CH4, H2, Oxygen (O2), nitrogen (N2), carbon monoxide (CO), and CO2.

SOFC set up & thermodynamic approach:

A SOFC test station was used to carry out the experiments. The methane rich gas was fed to the anode and the open circuit potential was logged. Methane must be reformed to hydrogen and CO before electricity can effectively be generated in an SOFC.

Results:

The main components in the sampled gas were methane and CO2 with concentrations of 71 and 23 mol%, respectively. Additionally, the recovered gas contained 9 ppm of hydrogen sulphide (H2S), which can permanently reduce the cell performance of an SOFC. Hydrogen sulphide was effectively removed (<0.1 ppm) with impregnated activated carbon

The use of CH4 recovered from the groundwater in an SOFC helps to mitigate the greenhouse gas emissions and improve the sustainability of DWTPs. The recovered methane gas of the Spannenburg DWTP can be used to run a 915 kW SOFC system. This can supply 51.2% of the total electrical power demand of the plant and decreases greenhouse gas emissions by 17.6%, which is around 1794 tons of CO2.

The annual power generation of the SOFC system can be 8 GWh, which is about 3 GWh more than that produced by an internal combustion engine such as a gas turbine or piston engine.

In the future, the researchers will conduct a long-term tests to determine the safe operating condition of SOFC with respect to the carbon deposition issue. These tests will be extended to the SOFC stack level and pilot plant (in the range of a few kW systems)

(Photo: Indiamart)

Reference: https://doi.org/10.1016/j.jclepro.2021.125877 (A solid oxide fuel cell fueled by methane recovered from groundwater, 2021)

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Light-driven process turns greenhouse gases into valuable products

Much research has been done in order to reduce the use of fossil petroleum products as fuels. In that respect syngas (synthetic gas) seems as a great opportunity for sustainable energy developments. Syngas is the mixture composed of hydrogen (H2) and carbon monoxide (CO) as its main components. It represents an important chemical feedstock used widely for industrial processes for generating chemicals and fuels:

Global use of syngas in industrial processes.

Syngas can be produced from methane (CH4) in a reforming reaction with water (H2O), oxygen (O2) or carbon dioxide (CO2). The process called methane dry reforming (MDR) can be combined with carbon dioxide:

CH4 + CO2 → 2 H2 + 2 CO

It is an environmentally friendly path, turning two greenhouse gases into a valuable chemical feedstock.

However, the MDR is process requires chemical catalysts and high temperatures in the range between 700 − 1,000°C. Usually, it suffers from coke deposition and, in consequence, catalyst deactivation.

Some chemists have recently demonstrated that light, and not heat, might be a more effective solution for this energy-hungry reaction.

The photocatalytic solution

A team of researchers at the Rice University in Houston, Texas, together with colleagues from Princeton University and the University of California have developed superior light-stimulated catalysts that can efficiently power MDR reactions without any heat input. This work has been published in the prestigious journal Nature Energy.

They have reported a highly efficient and coke-resistant plasmonic photocatalyst containing precisely one ruthenium (Ru) atom for every 99 copper (Cu) atoms. The isolated single-atom of Ru obtained on Cu antenna nanoparticles provides high catalytic activity for the MDR reaction. On the other side, Cu antennas allow strong light adsorption and under illumination and deliver hot electrons to ruthenium atoms. The researchers suggested that both, hot-carrier generation and single-atom structure are essential for excellent catalytic performance in terms of efficiency and coking resistance.

The optimal Cu-Ru ratio have been investigated in synthesized series of CuxRuy catalysts with varying molar ratios of plasmonic metal (Cu) and catalytic metal (Ru), where x,y are atomic percentage of Cu and Ru. Overall, the Cu19.8Ru0.2 was the most promising composition in terms of selectivity, stability and activity. In comparison to pure Cu nanoparticles, the Cu19.8Ru0.2 mix exhibits increased photocatalytic reaction rates (approx. 5.5 times higher) and improved stability with its performance maintained over 20 h period. Calculations showed that isolated Ru-atoms on Cu lower the activation barrier for the methane dehydrogenation step in comparison to pure Cu without promoting undesired coke formation.

In addition, the research has been supported by different methods (CO-DRIFTS with DFT) in order to unravel and prove single-atom Ru structures on Cu nanoparticles occurring in Cu19.9Ru0.1 and Cu19.8Ru0.2 compositions.

The comparison between thermocatalytic and photocatalytic activity at the same surface for MDR has also been demonstrated. The thermocatalytic reaction rate at 726°C (approx. 60 µmol CH4 / g / s) was less than 25% of photocatalytic reaction rate under white-light illumination with no external heat (approx. 275 µmol CH4 / g / s). This enhancement in the activity is attributed to the hot-carrier generated mechanism which is predominant in the photocatalytic MDR. The role of the hot-carrier is an increase in C−H activation rates on Ru as well as improved H2 desorption.

The scientists also reported the catalyst achieving a turnover frequency of 34 mol H2  / mol Ru / s and photocatalytic stability of 50 h under focused white light illumination (19.2 W / cm2) with no external heat.

As the synthesized photocatalysts is primarily based on Cu which is an abundant element, this approach provides a promising, sustainable catalyst operating at low-temperatures for MDR. This allows cheaper syngas production at higher rates, bringing us closer to a clean burning carbon fuel.

(Photo: Wikipedia)

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Energy storage in The Netherlands

Electricity Portfolio

In our previous blog post of the Frontis series on European energy storage markets we took a closer look at Spain. In our final post in this series we show where The Netherlands are positioned. The Netherlands are one of only two net gas exporting countries in the EU, along with Denmark. The domestic energy consumption reflects the abundance of the resource, with over 50% of electricity generated in the Netherlands coming from natural gas. With coal representing another 31%, the Netherlands are heavily centered around fossil-based electricity. Renewables represent less than 10% of electricity generated.

By 2020, renewable energy is to represent 14% of the entire Dutch energy supply, as mandated by the EU in the Renewable Energy Directive (2009/28/EC). This corresponds to an electricity sector with over 30% renewable energy generation.

There has been criticism directed towards the Netherlands for the progress made. According to projections in their 2009 National Renewable Energy Action Plan, the Netherlands should have reached nearly 20% renewable electricity in 2014. This lackluster progress prompted a statement from the EU Commission in its 2017 Second Report on the State of the Energy Union, where the EU Commission stated the Netherlands were the only member state to not exhibit average renewable energy shares which were equal or higher than their corresponding action plan trajectories in 2013/2014.

The EU Commission also stated that the Netherlands was one of the three countries (others: France, Luxembourg) with the biggest efforts required to fill 2020 targets.

Existing Energy Storage Facilities

To date, the Netherlands has almost 20 MW of energy storage capacity either operating (14 MW), contracted (1 MW), or under construction (4 MW).

All energy storage facilities in the Netherlands are electro-chemical, with the exception of the contracted 1 MW Hydrostar underwater compressed air energy storage project in Aruba (Caribbean). Hydrostar is a Canadian company specializing in underwater compressed air energy storage technologies.

The vast majority of the 20 MW of installed energy storage capacity in the Netherlands is spread over just three facilities: the Netherlands Advancion Energy Storage Array (10 MW Li-ion), the Amsterdam ArenA (4 MW Li-ion), and the Bonaire Wind-Diesel Hybrid project (3 MW Ni-Cad battery).

The Netherlands Advancion Energy Storage Array was commissioned in late 2015 and provides 10 MWh of storage to Dutch transmission system operator TenneT. The project, which represents 50% of all Dutch energy storage capacity, provides frequency regulation by using power stored in its batteries to respond to grid imbalances.

The 4 MW Amsterdam ArenA lithium-ion project was commissioned 2017 for PV integration and back up power purposes. The 3 MW Bonaire Wind-Diesel Hybrid project is a battery array located on the Dutch Caribbean island of Bonaire and used as a buffer between intermittent wind energy and the diesel-generation stations on the island.

The remaining 3 MW of Dutch energy storage projects are spread over 21 sub-100 kW facilities, mainly geared towards electric vehicle (EV) charging. Mistergreen, a leading developer of EV charging stations in the Netherlands has constructed 750 kW of LI-ion energy storage arrays at its various electric vehicle charging stations.

Energy Storage Market Outlook

Gearing up for significant market growth for electric vehicles in the Netherlands, there has been a considerable amount of effort to expand the country’s network of quick charging stations. This trend will have to continue in order meet the demand for the 1-million electric vehicles expected in the Netherlands by 2025, so one could expect that there will be large growth in the sub-100 kW Li-ion stations that have already started popping up around the country.

There is little information available regarding the need for large-scale energy storage but the overall need is likely low due to the low penetration of renewables in the electricity sector. However, there is significant focus on energy efficient/independent/self-sufficient housing.

Like Italians, the Dutch are very accustomed to using natural gas in their homes. This, coupled with the push for energy self-sufficient housing could present a unique market for residential power-to-gas systems in the Netherlands.

(Jon Martin, 2020, photo: Fotolia)

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Energy storage in Italy

Italy’s Electricity Portfolio

In our previous post we briefed you on the energy storage potential in the United Kingdom. With Brexit, Italy will become the third largest member state after Germany and France. With extensive mountain terrain in the north, Italy has long been dependent upon hydroelectric generation. Until the mid 1960s hydropower represented nearly all electricity production in Italy. The installed capacity of hydropower has been stagnant since the mid 1960s, with a rapid growth in fossil fuel based generation driving the overall share of hydropower fall from ~90% to 22% in 2014. A detailed breakdown of electricity sources in Italy is shown below.

Electricity Production in Italy (2014)

Considerable effort has been made to transition Italy to a low carbon electricity sector. As of 2016, Italy had the 5th highest installed solar capacity in the world and the 2nd highest per capita solar capacity, behind only Germany. In addition to its impressive solar progress Italy ranks 6th worldwide in geothermal with 0.9 GW.

Italy’s solar growth was propelled by feed-in-tariffs that wer enacted in 2005. This provided residential PV owners with financial compensation for energy sold to the grid. However, the feed-in-tariff program ceased on 06 July 2014 after the €6.7 billion subsidy limit was reached.

Even with its impressive accomplishments in renewable energy, traditional thermal generation (natural gas) still account for ~60% of total electricity generation in Italy. How much effort will go into reducing this number is still unclear. Italy has committed to 18% renewables by 2020 and is nearly 70% of the way there already so there is little urgency on reducing fossil-based electricity from the perspective of meeting this target. However, Italy is heavily reliant on fossil fuel imports (Deloitte) and energy security requirements will likely continue to push the development of more domestic electricity sources like renewables.

Energy Storage Facilities

Italy is dominating the electro-chemical energy storage market in Europe. With over 6,000 GWh of planned and installed electro-chemical generating capacity (~84 MW installed capacity), Italy is far ahead of 2nd place UK. This is largely due to the massive SNAC project by TERNA (Italy’s TSO), a sodium-ion battery installation totaling nearly 35 MW over three phases. A breakdown of energy storage projects, by technology type can be seen below.

Energy Storage Projects by Type (Sandia National Laboratories)

Service Uses of Energy Storage

In Italy, electrical energy storage is used almost exclusively for grid support functions; mainly transmission congestion relief (frequency regulation). While it may not be a direct case of renewables firming, congestion issues can be traced to the variability of solar power, meaning electrical energy storage development in Italy is largely driven by the need to integrate solar power.

Energy Storage by Service Use Type (Sandia National Laboratories)

Energy Storage Market Outlook

Italy is one of the top markets in the EU for energy storage and is primed for growth. The Italian TSO, TERNA, has been investigating selling energy storage as a service. In 2014 the AEEG, the electrical regulator under which TERNA operates, proposed that batteries should be treated as generation sources similar to cogeneration plants. Italy has always been a market completely dominated by a small number of big centralized utility companies and this trend is likely to continue when it comes to EES deployment. These companies have been focusing their efforts on battery technologies and are expected to continue down this path.

However, the private market could present great opportunity for P2G. The International Battery & Energy Storage Alliance have summarized the reality of Italy’s untapped energy storage market as follows: “With high solar output of 1,400 kWh/kWp, net residential electricity prices around 23 cent/kWh and currently no FIT, the Italian energy market is considered to be highly receptive for energy storage.”

Italy is now well-stocked with residential PV systems that can no longer collect subsidies. Combine this with the fact that the vast majority of homes in Italy burn natural gas imported from Russia, Libya and Algeria and it is clear that Italy presents a unique opportunity for P2G at a residential/community level. This is echoed by Energy Storage Update who in 2015 concluded that Italy was “one of the top four markets worldwide for PV-and-battery-based energy self-consumption.”

While it is unclear exactly how many residential PV systems there are in Italy, it was speculated in late 2015 that there were over 500,000 PV plants in Italy.

In our next post, we are looking at the situation for energy storage in Denmark.

(Jon Martin, 2019)