The Institute for Sustainable Process Technology (ISPT) has brought together various parties from different sectors of industry to study the storage of electricity in ammonia (NH3). Objective of this power-to-ammonia (P2A) study is to investigate under what conditions 1) NH3 can be produced using renewable electricity, 2) NH3 can be used to store electricity and 3) NH3 can be used as a CO2-neutral fuel for a power plant.
P2A is a partnership of ISPT, Stedin Infradiensten, Nuon, ECN, Technical University Delft, University Twente, Proton Ventures, OCI Nitrogen, CE Delft and AkzoNobel. This project has been carried out with Topsector Energy subsidy of the Ministry of Economic Affairs for conducting the power-to-ammonia feasibility study.
The electricity system is rapidly transforming towards a low carbon system, driven by ambitious CO2-reduction targets, decreasing costs levels for solar and wind and support schemes. Due to increasing deployment of variable renewable electricity sources (like wind and solar) in the electricity system, balancing supply and demand in the grids becomes increasingly challenging. By nature, intermittent renewable sources such as wind and solar are not always available. Therefore, fossil fuel fired power plants currently have an important function in balancing the electricity system.
However, keeping in mind the requirement for a deeply decarbonized economy in 2050, as globally decided at COP 2016 and in line with EU and Dutch energy policy, this fossil based solution will not hold anymore. Flexibility in the electricity system must be provided by CO2 free sources and at the same time the electricity system as a whole will have to further increase flexibility and arrange for sufficient short and long term (seasonal) storage of energy. The decarbonization of industry will lead to magnification of these effects caused by an unprecedented growth in electricity consumption.
NH3 is chosen as a potential contributing solution because it provides a pathway to fully CO2 neutral electricity storage and generation of CO2 neutral electricity on a scale that is not limited by scarcity of materials or storage space.
NH3, which is currently produced, as a base chemical and feedstock for fertilizers, in very large quantities from natural gas, is a high caloric energy carrier that can be produced from renewable electricity and thus be used to store electricity. Water is electrically split into hydrogen (H2) and oxygen, subsequently the H2 and nitrogen from air are converted into NH3. NH3 has a potential to be used as a chemical storage medium due to high efficiency, energy density and low cost of nitrogen sourcing. A concern is the safe handling of NH3, however with the large amount of experience in the chemical industry this appeared very well manageable.
Using NH3 as potential solution gives rise to questions like what is the attractiveness of NH3 as a chemical storage medium? Can power-to-ammonia create enough flexibility on the one hand and avoid grid capacity increase and integration costs on the other hand? Subject of this study is to investigate both technological and economical under what conditions NH3
can be produced using renewable electricity;
can be used to store electricity;
can be used as a fuel for an electricity production facility.
The partners in this project have studied three cases. The first case relates to electrochemical production, storage and use of NH3 for a rural setting (Goeree-Overflakkee), avoiding grid modification costs and allowing local production of CO2 free NH3. The second case allows use of NH3 as a CO2 neutral fuel in the highly efficient Nuon Magnum gas turbine combined cycle (CCGT) power plant in the Eemshaven, thus generating flexible and CO2 free electricity. The third case assesses the electrochemical production of NH3 at OCI Nitrogen to replace (some of) the current, natural gas based production. Apart from assessing the economic feasibility of the above options, other relevant aspects related to power-to-ammonia including technical, operational, financial, legislative and safety issues have been evaluated as well.
We have concluded that CO2 neutral NH3 produced in an electrochemical way from sustainable electricity will be a feasible alternative for NH3 produced from natural gas in the longer term.
Comparing the processes for electrochemical production of NH3 resulted the following ranking in decreasing order of efficiency; Solid Oxide Electrolytic Cell (SOEC), Low Temperature Solid State Ammonia Synthesis (LT SSAS), Battolyser, Proton Exchange Membrane (PEM) and High Temperature SSAS (HT SSAS).
A competitive price for electrochemically produced CO2 neutral NH3 versus conventional natural gas based produced NH3 (300-350 EUR/ton) can be achieved when investment costs for electrolysers drastically come down, when costs for emitting CO2 increase significantly and when there is sufficient supply of relatively cheap CO2 free electricity. The high investments in electrolysers require a large on-stream time to minimize costs per ton. This contradicts with the intermittency of large scale availability of renewable energy due to the production patterns of wind and solar.
Use of NH3 as a fuel in a CCGT power station is possible by cracking the NH3 into H2 and nitrogen before combusting the H2 in the gas turbine. Time to market for large scale application is estimated to be 5-10 years. As the NH3 will be cracked into H2 prior to combustion in the gas turbine, application of NH3 as a fuel in the power sector enables a seamless integration with a H2 economy. Use of NH3 as CO2 neutral fuel in the Nuon Magnum power station has the potential to reduce CO2-emissions by 3.5 Mton/year when operating on base load producing 10 TWh of electricity. This reduction is 7% of the power related carbon emissions in The Netherlands in 2015.
Locally produced CO2 neutral NH3, as investigated in the Stedin case on Goeree-Overflakkee, will be sold on the market. The distribution of the NH3 can be done via the NH3 terminal in the harbour of Rotterdam.
Production of NH3 using (excess) renewable energy cannot compete with existing fossil based NH3 production. Drastic changes in production cost of electrolysers to less than 70% of the reference price of 1000 EUR/kW, supply of renewable energy and a global increase in CO2 price are needed to make this a competing production route.
Reduction of the CO2 footprint of NH3 by producing it via electrochemistry rather by the conventional process from natural gas is only possible if the electricity used is renewable. In that case the CO2 footprint is zero. If electricity produced from fossil fuel is used for the electrochemical production of NH3, the CO2 footprint will increase by approximately a factor 3.
For grid owners, an advantage of producing NH3 with wind and solar power will be that investments in the grid can be reduced. If the share of wind and solar power increases without demand side management and without energy storage the investment requirements in increasing grid capacity will be substantial. The combination of demand side management and local energy storage can contribute to the reduction of the necessary investments in the grid. Power-to-ammonia enables energy to be transported and stored for periods of days, weeks or even months.
Electricity storage in the form of NH3 will add cost to the overall electricity system. However, large scale CO2 neutral energy storage will introduce important benefits for the system, enabling a further penetration of intermittent renewable electricity sources, enabling further electrification and providing CO2 free NH3 as fuel and chemical commodity.
At deep decarbonisation, flexible electricity production based on application of fossil fuels during periods when supply from intermittent renewable sources is insufficient, cannot be applied unless Carbon Capture and Storage will be deployed. In other words, the initially more costly use of NH3 as a CO2 neutral fuel for electricity production becomes very attractive and one of the few realistic alternatives.
Only installing additional renewable wind and solar capacity is not sufficient to meet the CO2 reduction targets of 80-95% in 2050. Large scale storage and import of renewable electricity is required to meet these targets. Power-to-ammonia enables both storage and import and has the potential to contribute substantially to CO2 reduction targets, offering flexibility for the electricity system and allowing for an alternative to investments in electricity grid infrastructure.