Flexible operation of electrolyser at the garage forecourt to support grid balancing and exploitation of hydrogen as a clean fuel

Abstract

Rapid growth in the generation of renewable energy (RE) and its integration with electricity grids has been driven by concerns about both the climate impacts and the depletion of fossil fuels. Moreover, these concerns have prompted the need to develop alternatives to hydrocarbon fuels, leading to the expectation that fuel cell vehicle numbers will similarly increase. However, the variable and intermittent output of RE generators significantly affects the capability for electricity networks to balance supply and demand, although this may be addressed through energy storage and demand-side response (DSR) technologies. One potential DSR technique that can be implemented at industrial scale is water electrolysis, which is used for hydrogen production. When electrolyser operation is modulated, for example, to respond to the variable output of wind and solar power sources, it can be exploited as a dispatchable demand load. Naturally, this would need to be incentivized by electricity tariff structures that reflect the dynamics of RE availability. This paper aims to compare the economics of continuous and dispatchable electrolyser operation for producing affordable hydrogen at garage forecourts in Libya, while ensuring no interruption in the fuel supply to vehicles. Using the coastal city of Derna as a case study, with renewable energy generated by a wind farm, a suitable turbine specification and the number of turbines needed to meet demand was determined through an analysis of wind speeds. The constantly varying difference between RE power supply and electricity demand on the grinded the surplus power at any given time. Using a linear programming algorithm to optimize the hydrogen cost, based on the current price of electricity, this study examines a hydrogen refuelling station in both dispatchable and continuous operation. As the capital cost is already known, the optimisation focuses on the variable cost in order to reduce the price of hydrogen, which means using the cheaper of two electricity tariffs. Three scenarios were considered to evaluate whether the cost of electrolytic hydrogen could be reduced through using lower-cost off-peak electricity supplies:1- Standard Continuous, in which the electrolyser operates continuously on a standard tariff of $16/kWh.2- Off-peak Only, in which the electrolyser operates only during off-peak periods at the lower price of $7/kWh.3- 2-Tier Continuous, in which the electrolyser operates continuously on a low tariff at off-peak times and a high tariff at other times.The results indicate that Scenario 2 produced the cheapest electricity at $3.89 per kg of hydrogen, followed by Scenario 3 at $5.10 per kg, and the most expensive was Scenario 1 at $9.26 per kg.