Effect of electricity tariffs and cooling technologies on dairy farm electricity consumption, related costs and greenhouse gas emissions

The aim of this study was to provide insight into the variations in dairy farm electricity costs across five electricity tariffs. The effect of four milk cooling scenarios is also simulated to illustrate the effect of technologies on the electricity consumption, related costs and CO2 emissions of a dairy farm. Helping dairy farmers to make informed business decisions when confronted with future options in the sphere of electricity tariffs and energy efficient cooling systems will contribute to optimum farm profitability and will help to improve the profitability and sustainability of the industry. A previously developed model capable of simulating electricity consumption, related costs and CO2 emissions of dairy farms was used to simulate five electricity tariffs (Flat, Day&Night, Time of Use Tariff 1 (TOU1), TOU2 and Real Time Pricing (RTP)) on a dairy farm with 195 milking cows. The Flat tariff consisted on one electricity price for all time periods, the Day&Night tariff consisted of two electricity prices, a high rate from 09:00 to 00:00 h and a low rate thereafter. The TOU tariff structure was similar to that of the Day&Night tariff except that a third peak price band was introduced between 17:00 and 19:00 h. The RTP tariff varied dynamically according to the electricity demand on the national grid. The model used in these simulations is a mechanistic mathematical representation of the electricity consumption that simulates farm equipment under the following headings; milk cooling system, water heating system, milking machine system, lighting systems, water pump systems and the winter housing facilities. Direct expansion, ice bank and pre-cooling milk cooling systems were simulated to determine how dairy farm electricity consumption, related costs and CO2 emissions vary according to the milk cooling system installed on the farm. Annual simulated electricity consumption of the farm was 32,670 kWh when a direct expansion milk cooling system without pre-cooling of milk was included in the model. The annual electricity consumption of the farm on the day & night tariff was €4,571. Adding precooling with ground water to the direct expansion milk cooling system reduced annual electricity consumption by 28% to 23,660 kWh and reduced annual electricity costs by 38% to €2,875. The addition of a pre-cooling system to the direct expansion milk cooling system saved 3,973 kg of CO2. Simulation of an ice bank milk cooling system without pre-cooling resulted in annual simulated electricity consumption of 34,777 kWh. The annual electricity consumption on the day & night tariff was €3,793. Adding pre-cooling with ground water to the ice bank milk cooling system reduced annual electricity consumption by 30% to 24,181 kWh and reduced annual electricity costs by 33% to €2,527. The addition of a pre-cooling system to the ice bank milk cooling system saved 5,044 kg of CO2.