Objective
To demonstrate the use of ice storage/hydro-cooler technology in a brewery for the total cooling during the continuous (24 hours per day) Fermentation Process and to show a 25% improvement in refrigeration efficiency with substantial energy cost and electrical maximum demand savings.
To also demonstrate the use of chilled water at less than 1 deg. C to replace the present secondary refrigerant, Alcohol (containing 4% Methanol) circulated at sub zero temperatures and to improve the safety of the system on a site with limited space where the ice storage units will need to be positioned on the Brewery roof.
The total system is innovative in that this will be the first time that ice storage has been applied to satisfy the total fermentation cooling requirement in a brewery.
The introduction of ice storage/hydro-cooler technology into a brewery for total fermentation cooling having a continuous 24 hours/day duy and showing a 25% improvement in efficiency with substantial energy costs and electrical maximum demand saving benefit has been successfully proven.
The project was a complete technical success where the energy saved and transferred objectives were achieved as follows :
FORECAST ACTUAL
kWh Saved in Total 400,000 431,000
kWh Transferred (Day to Night) 900,000 819,000
There was a slight reduction in the kWh's transferred, however, this was partly due to the increase in the total kWh's saved.
The installations has operated since entering normal service without any modifications or alterations and is now an integral part of the brewery cooling system.
In terms of load spreading, the installation of the 'cold' storage system has reduced the brewery electricity maximum demand from 2.25 MW to 1.68 MW, a 600 kW reduction. A much improved electrical profile now exists.
The annual electricity operational cost for the total refrigeration/cooling plant is now IRL 77,000; this compares with the previous costs at IRL 158,500 annum, giving an annual cost saving benefit IRL 81,500.
The Simple Payback for the project was 4,87 years, however, it is expected that future installations could expect payback periods of 3 to 4 years for retro-fits. Where new plants are being considered or additional capacities are necessary, the return on the capital could be as low as 1 to 2 years. In some cases for new plant installations, there may be no additional capital necessary over and above a conventional plant dependent on the actual design layout.
Traditionally in the brewing industry there are two cooling systems; a high temperature circuit and a low temperature circuit, both utilising ammonia as the primary refrigerant and industrial alcohol as the secondary. The low temperature circuits are utilised for cooling down to zero and below temperatures, mainly for storage purposes in cold rooms, however, the high temperature circuits are for above zero temperatures and in particular for the heat removal created during fermentation. The majority of the cooling requirements at the St Francis Abbey Brewery are for above zero temperatures.
The design involves the complete change over from alcohol to water for the high temperature secondary refrigerant system.
The ice storage units are to be installed in parallel and piped to the H.T. Storage vessel, now isolated from the L.T. Vessel, including circulating pump set and non-return valves. The return pipe is raised to a height greater than the highnest point in the existing secondaryrefrigerant circuit and complete with a siphon breaker/vent. With the new arrangement, the existing vent/fill line is to be isolated. The primary refrigerant circuits for Compressors 1 and 2 are to be altered to feed the 2 - ice storage units. Branch connections from the discharge lines on the individual shell and tube condensers are to be piped to the ice storage unit surge drums situated above the coils. The suction line returns are to be fitted into the existing suction pipework immediately before the compressor inlets. The existing discharge and suction lines are to be fitted with isolating valves.
The control system is to be arranged so that the main chilled water pumps, between the storage unit and H.T. Vessel, continuously operate. The existing distribution pumping sets are to be selected automatically by the present control system on demand for process cooling.
The ice build period will be between 2300 hours and 0800 hours (9 hours) the off-peak cheap rate period daily, during which time No 1 and No 2 compressors will operate until 50 m thickness of ice is achieved or 0800 hours, which ever is sooner. The maximum storage capacity for the installation is 7600 kW (6.5 million Kcals). From 0800 hours every morning the cooling requirements are to be satisfied by the melting of ice.
The Construction Phase of the project will take 7 months to complete including commissioning. A 12 months Evaluation Period will follow where the installations operating conditions are to be closely monitored and the performance characteristics checked.
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DEM - Demonstration contractsCoordinator
8 Dublin
Ireland