Power systems for dairy sheds : an investigation into the right mix of energy efficiency, load shifting and energy supply technologies : submitted as partial fulfilment of a Masters of Technology endorsed in Energy Management
This study investigated the potential for using stand-alone power systems for dairy milking
sheds in New Zealand.
The study was in two parts:
designing a typical load profile for a dairy shed and evaluating changes that could be
made to the dairy shed to improve energy efficiency or shift load, using a mechanistic
using the optimisation modelling tool HOMER Pro to find the best configuration of
power system, energy efficiency and/or load shifting improvements of a solar-diesel
hybrid power system and a solar-diesel-biogas hybrid power system.
The study found that milk vat insulation, variable speed drives and generator heat recovery
were good investments to reduce power system costs. The high capital cost of ice banks
made them less attractive for herds less than 370 cows. Superheat heat pumps and biogas
systems were poor investments and increased costs in most cases when compared with the
base scenario. While there was variation within the regions, overall the optimal system,
when sensitivity scenarios were accounted for, was found to be similar between the three
regions studied with the Bay of Plenty having the lowest overall costs followed by Taranaki
and Manawatu. Sensitivity scenarios showed bias against deferrable loads such as ice bank
refrigeration systems, hot water storage systems and the pumping of effluent. Diesel prices
had a greater effect where the renewable fraction was low. Increasing diesel prices resulted
in larger PV arrays and batteries.