Abstract
As countries seek to meet climate change mitigation obligations and integrate high levels of variable renewable generation into electricity systems, opportunities for flexible demand are increasingly being sought to provide a cost-effective approach to balancing electricity grids. In New Zealand, the dairy farming sector has the capacity to shift electricity demand out of peak periods to help balance grid demand. Case study research on a group of large dairy farms shows that while milking and irrigation demand do contribute to peaks in local and national electricity demand, they can also reduce peaks and utilise energy at other times of day.
Electricity demand data from six of the farms and the three main irrigation pumping sites on the farms were collected at 30-minute resolution for one year. Daily profiles of electricity demand were analysed to show the contribution of milking and irrigation demand to peak electricity demand and to determine the impact of adopting time-of-use (TOU) pricing on the farm’s electricity costs. With the introduction of TOU pricing, 20% of the dairy shed's daily electricity costs are attributable to the 2.5-hour morning peak period. Irrigation would need to operate with much greater flexibility under a TOU price than its existing process of load shedding during intermittent network peaks.
Farmer interviews are used in combination with electricity demand profiles to estimate the demand from groups of appliances in the milking sheds. These disaggregated loads are presented as a block diagram of electricity demand to explore the impacts of changing milking times or changing appliance use within the milking shed. Two options to reduce peaks in electricity demand based on a practice change to Once-A-Day (OAD) milking and an alternative model of maximum load shifting without altering milking practices are presented as examples of alternative milking shed demand.
Using thermal and pumped water storage to shift electricity demand away from milking periods could reduce milking electricity costs by 9% under a TOU pricing regime; under a capacity-based pricing regime, load shifting could reduce milking electricity costs by 46%. Once-A-Day milking achieves an 18% reduction under TOU, mostly due to reduced overall demand, and capacity requirements are reduced by only 8%.
These findings demonstrate the value of simple tools in comparing scenarios. They can enable consumers to explore the impact of changes in their electricity use to make targeted energy efficiency improvements and shift loads to reduce their contribution to peaks.