solar hot water reduces costs in the dairy - Dairy Sustainability Website

Solar hot water reduces
costs in the dairy
Sustainable Farming Systems
The Farm
Mark and Joanne Seng
Blenheim, South-East Queensland
With electricity costs set to rise by more
than 60% over the next three years,
Blenheim dairy farmers Mark and Joanne
Seng are ensuring their business remains
profitable by improving efficiencies and
reducing farm input costs. Solar hot water
is just one part of this strategy.
Choosing solar
The Sengs decided to replace an old
inefficient electric hot water system used
for cleaning milking equipment at the
same time as a new milk vat was installed
in the dairy.
At first, Mark thought a heat recovery
pump might be the best option, using heat
generated from the milk vat cooling system
to heat the water for the dairy. Although
heat transfer pumps are an excellent way
to save energy costs, he was advised
that the new milk vat cooling system was
possibly too efficient, and cooled the
milk too rapidly to create enough heat
energy to meet the hot water requirements
for the dairy.
A solar hot water system was
recommended by the milk vat supplier as
a better alternative for the Sengs’ situation.
Selecting the system
Mark considered a number of domestic
solar hot water units before settling on
an Apricus solar hot water system. This
system uses new technology – consisting
Business snapshot
• Herd size: 80-100 Friesian and
Jersey milkers
• Farm size: 202 ha
• Production: About 600,000
litres a year
• Calving: Year-round
• Soils: Sandy loam scrub soils
and dark clay creek flats
• Pasture: Rhodes grass,
lucerne and rye grass
• Supplementary feed: Mix of
brewers’ grain and homegrown
sorghum or maize
silage twice daily
• Water: Only a limited amount
of irrigation water is available
from farm dams and bores
Mark Seng has installed a solar hot water system and a new milk vat at the dairy.
Lessons learned
• A domestic solar hot water
system meets the dairy’s needs.
• Using the correct water
temperature is important
for effective cleaning and to
minimise water and energy use.
• Rebates and subsidies reduce
installation cost.
• System should pay for itself
in energy savings in less than
15 years.
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of an array of 30 absorber tubes which
concentrate and transfer heat to a
collector manifold – to collect the sun’s
energy. Water is pumped through the
manifold when the water temperature
in the manifold is higher than that of the
storage tank. The round surface allows the
absorber tubes to passively track the sun,
ensuring greater solar performance. The
manufacturers claim the system is highly
efficient, even in extremely cold areas.
If the water temperature gets too high, the
circulation pump shuts down so no further
heating or damage to the unit occurs.
To ensure there is adequate hot water on
overcast days, the 315-litre storage tank is
equipped with an electric booster element
which is only activated at night on off-peak
power, if required.
The collector weighs only 120 kg and
can be installed on most roofs without
extra support. Due to the evacuated tube
system’s design, cleaning or maintenance
are rarely needed.
The only modification required to
this domestic system was to omit a
temperature limiting valve, a safety
requirement for domestic hot water
systems. To reduce heat loss and further
improve efficiency, all copper pipes
between the collector the storage tank and
the outlet taps are well insulated
Water and energy use
Mark minimises water and energy used
in the dairy by using only registered
cleaning agents and recommended water
temperatures for each agent. Overheated
water not only increases energy costs,
but can reduce the effectiveness of the
The round absorber tubes passively track the sun.
Water and temperatures used for cleaning the milking machine and vat.
Purpose Total water used Hot water
L/day
cleaning agent and can result in high Total
Plate Counts (TPC).
The Sengs use a total of 119 litres of
hot water in the dairy per day, including
cleaning the milking machine and vat.
Correct water temperatures are important
for effective cleaning results.
The new Westfalia Surge milk vat has an
automated self-cleaning system with an
independent hot water system which was
fed by cold water directly from the rain
water tanks. To further reduce the energy
bill, Mark has modified the plumbing so
that all hot water is heated by the solar
system first.
Costs, rebates and subsidies
The unit was bought from Solar
Distributers, Toowoomba, in late March
2010. The costs (excluding GST) were:
Unit cost $4,300
Roof frame $300
Installation $1,993
Total cost $6,593
RECs (35@$36) - $1,250
Balance $5,345
The number of eligible RECs varies and
depends on the brand and model of the
system, the installation date, the location,
and the market value of RECs on the day.
This will all be much simpler from January
2011 when the Australian Government is
fixing the up-front subsidy at $40 per REC
for all solar panels and solar hot water
systems. A typical domestic size hot water
system will be eligible for $1,200 (Refer to
website www.orer.gov.au for more details).
The Sengs were also eligible for a $2,800
grant through their involvement in the
Lockyer Dairying Better ’n Better for
Tomorrow group and a sustainability
project funded by Landcare Australia and
Woolworths.
Effectiveness and savings
The solar hot water system has proven
to be highly efficient with the water
temperature reaching 82°C without the
use of electricity when it was installed in
March 2010. Previously around 4,000 kW
per year of electricity was used for hot
water in the dairy, costing $280 on a night
rate of 6.99 ¢/kW hr.
Mark expects at least 15 years of reliable
service from the solar hot water system,
and with electricity costs expected to rise
by 60% over the next three years, the
Sengs should save at least $360 per year
on power bills or $5,400 over the life of the
unit (based on 80% solar energy used).
The solar hot water system should pay for
itself, a good outcome considering the old
system was due for replacement anyway.
Useful websites
The Office of the Renewable Energy
Regulator: www.orer.gov.au
DairySA Fact Sheets: www.
dairyingfortomorrow.com/index.
phpid=52 on heating water, cooling milk,
water in the dairy and renewable energy
sources
contact
Dairying for Tomorrow Coordinator at the
Queensland Dairyfarmers’ Organisation
on (07) 3236 2955, mobile 0427 669 994
or e-mail nrm@dairypage.com.au
Temp
C°
Milking machines 60 L twice daily after milking using Dasco – Klenz in One 60 38-40
Caustic hot wash 70 L once each week using DeLaval - PowerPack 10 70
milking machines
Milk vat wash 250 L/wash every second day 49 65
Total dairy 165 L/day 119
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