Impact of Energy Efficiency Impact of Energy Efficiency Improvements on Water Improvements on Water

Heating Costs on New Zealand Heating Costs on New Zealand Dairy FarmsDairy Farms

Dale Eastham – P G Dip candidateDale Eastham – P G Dip candidate

SummarySummaryThis project is one of five projects of an energy assessment programme.

During this research project data will be collected from several milking sheds, including Massey’s number Four Dairy Farm. The data will be analysed to determine how much electricity is used to heat water used in the shed.

Three methods of reducing the amount of power required will be assessed.

Batch heating

Timer installation to control when water is heated

Re-routing excess heat energy (theory or practice)

SituationSituationDairy farms are heavy consumers of electricity. Most electricity is consumed in the dairy shed by vacuum lines, milk chilling, water heating, and pumping milk and water.

These activities consume varying proportions of power depending upon the system design of the milking operation.

On Massey’s Number Four Dairy farm, water heating consumes 25-30% of the electricity use alone.

There are many ways of reducing the amount of electricity consumed to heat the water needed on a daily basis. However, finding a method that is cost-effective, practical for a dairy shed situation, and has an acceptable payback period for the farmer is difficult.

Little work has been done previously on developing systems for helping the individual dairy farmer to solve these problems.

Project AimProject Aim

To report on the energy requirements of To report on the energy requirements of alternative cost reduction methods to water alternative cost reduction methods to water heating in dairy sheds.heating in dairy sheds.

ObjectivesObjectives Install data loggers to record the amount of Install data loggers to record the amount of

electrical power used in Massey’s number Four electrical power used in Massey’s number Four dairy farm for hot water heating.dairy farm for hot water heating.

Collect, interpret and report on the data from the Collect, interpret and report on the data from the loggers installed on the relevant machinery.loggers installed on the relevant machinery.

HypothesisHypothesis

Savings will be achieved by only heating the Savings will be achieved by only heating the amount of water required for operating the dairy. amount of water required for operating the dairy.

Savings will be achieved by installing a timer on Savings will be achieved by installing a timer on the heating element will eliminate ‘maintenance the heating element will eliminate ‘maintenance heat’ requirements.heat’ requirements.

Savings will be achieved by modifying the shed’s Savings will be achieved by modifying the shed’s systems to allow excess heat energy to be re-systems to allow excess heat energy to be re-used in other systems around the shed.used in other systems around the shed.

MethodologyMethodologyData recorders have been placed in several Data recorders have been placed in several dairy farms around the Manawatu since the dairy farms around the Manawatu since the past summer.past summer.

Loggers are attached to selected appliances to Loggers are attached to selected appliances to measure and record the electricity used.measure and record the electricity used.

The water heating data from these loggers will The water heating data from these loggers will be evaluated and the system modified and the be evaluated and the system modified and the data will be recorded for another four weeks data will be recorded for another four weeks and then reviewed again.and then reviewed again.

Hot water tank temperatures Hot water tank temperatures (76 days)(76 days)

30

40

50

60

70

80

90

0:00 2:00 4:00 6:00 8:00 10:00 12:00 14:00 16:00 18:00 20:00 22:00 0:00

Time of Day

Tan

k T

emp

(d

eg C

)

LimitationsLimitations

Budgetary constraints - some Budgetary constraints - some machinery that could be useful is machinery that could be useful is currently hugely expensive (Mohana currently hugely expensive (Mohana Blue and DTS).Blue and DTS).

Time constraints - deadlines set Time constraints - deadlines set down by the projects financial down by the projects financial backers.backers.

Continuous Heating- the Continuous Heating- the present situationpresent situation

After a hot wash cycle no more hot water is After a hot wash cycle no more hot water is immediately available for extra washing.immediately available for extra washing.

Installing a timer controlling when water is Installing a timer controlling when water is allowed into the cylinder via a solenoid would allowed into the cylinder via a solenoid would solve this problem by acting as an indirect solve this problem by acting as an indirect heating element control timer.heating element control timer.

This creates a batch-heated, drain-down hot This creates a batch-heated, drain-down hot water system, opening up various heat recovery water system, opening up various heat recovery and timing options.and timing options.

Waste Heat RecoveryWaste Heat Recovery

Waste water is put through heat Waste water is put through heat exchangers once prior to dumping it.exchangers once prior to dumping it.

Warm water is circulated slowly Warm water is circulated slowly through exchangers (requiring through exchangers (requiring separate pump and storage tanks).separate pump and storage tanks).

4 Main sources for recovering 4 Main sources for recovering waste heat energy have been waste heat energy have been

identifiedidentified

Warm milk en route to the storage vatsWarm milk en route to the storage vats

Vacuum pump discharge airVacuum pump discharge air

Hot-wash waste waterHot-wash waste water

Milk chilling equipmentMilk chilling equipment

Warm Milk Heat RecoveryWarm Milk Heat Recovery

2-3 times the volume of warm milk as volume 2-3 times the volume of warm milk as volume of hot water needed is available, meaning of hot water needed is available, meaning there is sufficient heat energy in the system.there is sufficient heat energy in the system.

But this heat is only available But this heat is only available immediatelyimmediately before hot water is needed.before hot water is needed.

This could necessitate storing This could necessitate storing the hot water until the next the hot water until the next milking, meaning additionalmilking, meaning additionalcosts.costs.

Vacuum Pump Discharge Air Vacuum Pump Discharge Air Heat RecoveryHeat Recovery

Could be put straight into a heat Could be put straight into a heat exchanger but using a heat pump exchanger but using a heat pump first to concentrate the heat energy first to concentrate the heat energy would be needed to take full would be needed to take full advantage of this source.advantage of this source.

Even so, it would still be subject to Even so, it would still be subject to the same timing problem as before.the same timing problem as before.

Milk Chilling Equipment Heat Milk Chilling Equipment Heat RecoveryRecovery

Waste heat source with the most Waste heat source with the most potential.potential.

Heat will be taken from the Heat will be taken from the refrigeration unit by a desuperheater refrigeration unit by a desuperheater e.g. DTS, Mohana Blue. e.g. DTS, Mohana Blue.

Regardless of method, energy input is Regardless of method, energy input is needed to raise the water temperatureneeded to raise the water temperature

These methods lead to a significant reduction These methods lead to a significant reduction in energy input costs needed for water in energy input costs needed for water heating.heating.

Shifting the heating load to night time Shifting the heating load to night time electricity rates has the potential to halve this electricity rates has the potential to halve this cost again.cost again.

Additionally, delaying the heating process to Additionally, delaying the heating process to just before milking will eliminate maintenance just before milking will eliminate maintenance heating costs and losses.heating costs and losses.

Other possible measuresOther possible measures

Using one large tank sufficient for the Using one large tank sufficient for the entire days’ hot water needs would entire days’ hot water needs would lose less heat through irradiation lose less heat through irradiation than multiple, smaller tanks.than multiple, smaller tanks.

Insulating the hot water Insulating the hot water cylinders in any way would cylinders in any way would further reduce heat loss.further reduce heat loss.

SupervisorsSupervisors

Chief Supervisor: Prof. Ralph SimsChief Supervisor: Prof. Ralph Sims

Co-supervisor: Karl HartmanCo-supervisor: Karl Hartman