Power systems large installed capacities of wind power relative to their maximum demand present grid-integration issues. For instance if at any time wind power plant (WPP) generation exceeds that which can be safely absorbed by the system, some of the available wind input needs to be curtailed. Wind curtailment (WC) diminishes the financial capacity of existing WPP, reduces incentives to deploy new wind capacity and inhibits the production of low-carbon electricity thus penalizing efforts to achieve high wind penetrations. The value of wind penetration (ΦW) at which curtailment measures need to be taken depends on the design and characteristics of the specific power system, but a penetration limit (PL) of 20% to 30% of total system demand is typically appointed for islanded power systems without significant interconnections. Solutions are therefore required to facilitate the achievement of high wind penetrations. One solution is to deploy electrolysers (ELS) next to the main WPP. In combination with hydrogen storage systems, ELS can be used for hydrogen production during periods of excess wind supply and low electricity demand. By allowing electrolysers to absorb the surplus wind output WC can then be reduced and ultimately eliminated while maintaining security criteria in the power system.
An economic assessment has been carried out to explore the benefits of a large deployment of ELS in the power system to mitigate WC. A preliminary estimation has been made on the amount of wind energy that would be rejected and the subsequent income loss associated for 20% ≤ ΦW ≤ 100%. Also an economic analysis is carried out to assess the benefits of deploying a large electrolyser stock to absorb the WPP generation otherwise curtailed. The main outputs are: (i) ratio of electrolyser capacity to wind capacity installed required for eliminating different levels of WC; (ii) total capital cost and annualized cost of hydrogen production plants; (iii) hydrogen production costs ($ / kg) and (iii) pay-back periods assuming a range of electrolyser capital costs (CELS) and efficiencies (µELS) . Results are presented for a hypothetical islanded power system based on wind generation and demand data for Denmark.
It is found that WC and revenue loss associated increase drastically as ΦW increases. At ΦW = 50% revenue losses for WPP operators are between 20% and 47% of net annual revenues depending on PL. The objective of complete elimination of wind curtailment requires rather large ELS capacities and entails low utilization factors since the wind power absorbed would rarely equal the rated capacity of the electrolyser stock. There is a trade-off between the sizing of the electrolyser stock and the capturing of the wind resource available. Maximum economic benefits are attained when the electrolyser stock is sized to capture around 50% of WC and it is possible to produce H2 from WC at ≤ $5 / kg (plant gate including compression and storage at 200 bar) for ΦW ≥ 30% if CELS < $500/kW and µELS > 60%. Hydrogen production costs of ≤ $3 / kg can be obtained at ΦW ≥ 60%. Average pay-back periods for the additional investment in H2 production plants are < 10 years at ΦW > 30% if CELS < $500/kW and µELS > 60%. Depending on the market values of hydrogen and electricity, optimum cost and performance parameters can be found to maximize the economic value of WPP and ELS at high ΦW.
