Improve efficiency of cooling systems

Step by step Audit Map cooling system Identify energy consumption of cooling system Evaluation of existing cooling system Verify cooling load Identify saving measures

Energy schema Energy schema of a 2.2 kW freeze facility

Map cooling system I

Map cooling system II

Manufacturers data Cooling capacity (kW) Vaporizer capacity (kW) Electrical input power (kW) Condenser power (kW) Performance (COP) Mass flow (kg/h) Volume flow of oil cooler, power (m3/h, °C, kW) Operation limits (condensation temperatures max, min), evaporating temperatures (°C)

Additional components

Temperature levels

Additional data to measure

Evaporation and condensation charts Evaporation and condensation charts of individual cooling liquids help to identify evaporation and condensation temperatures at given pressure Most pressure manometer measure gauge pressure in relation to ambient pressure – both pressure levels need to be added to achieve absolute presure On site measurements to be conducted by using Schrader valves Evaporation and condensation charts to be obtained from http://en.ipu.dk/Indhold/refrigeration-and-energy- technology/coolpack.aspx

Calculating the energy consumption Assumption: A cooling plant operates at 60%. ECcooling system = (Pcomp *0.6 + Pp,c,o * 0.9+ PL,c,o * 0.9) * BZ Alternatively it is possible to calculate the full load operating time (part time operations will be calculated in full load operating times, e.g. 2 hrs part load gives one hour full load) ECcooling system = Pcomp*FLH + Pp,c,o*FLHp + PL,c,o * FLH l,c,o A cooling plant operates at 60%. This is an average value and can strongly vary for a concrete plant (+/-50%) ECcooling system = Energy consumption FLH = Full load hours

Full load operating times

Calculating energy consumption with cooling load Energy consumption compressor = Qo (Cooling load) / Coefficient of Performance * Running Time

Outdoor temperature variation in Austria over one year Frequency scale temperature

Calculating energy consumption with load profile

Energy consumption with measurements

Example measured energy consumption hotel 2 compressors Deep cooling: compressor 16kW, R404A, -38°C (7,047 h FLO); on/off General cooling: compressor 25kW, R134a, -10°C (4,274 h FLO) (piston bypass) Direct evaporation, pumps: 4kW; fans: 16kW (1,964 FLO); on/off Electricity consumption cooling area includes: Lighting, fans, electrical deicing, heating windows, door heating, heating condensate

Break down electricity consumption

Coefficient of Performance Q = the heat supplied to or removed from the reservoir P is the work consumped by the compressor

Losses

Cooling rooms – area of losses

Operating figures

Energy saving opportunities I Switch off cooling chamers not in use Check if cooling temperatures can be adjusted (increased): Storage temperature recommendations Check factors which request max. temperatures Check storage procedures: Cooling chain must not be interrupted Seal pass between lorry and cooling chamber Avoid to intermediate store in warm rooms

Energy saving opportunities II Check for opportunities to use waste heat Free cooling: freshly cooked products not directly in storage rooms; pre-cool with ambient air (check hygiene standards

Energy saving opportunities III Reduce heat input through doors Staff training: close doors Alarm after predefined periods Check, clean and exchange door seals Automatic door closing device (€ 120) Install plastic curtains

Insulation Recommended U-values and insulation thickness for storage rooms for general cooling / deep cooling: 80mm and 170mm PUR Continuous termal imaging to identify losses and thermal bridges Avoid cable ducts / ventilation ducts leading through cold rooms

Reduce waste heat caused by illumination LEDs (E27) can replace incandescent lamps used in deep cooling chambers Ballasts to be installed outside the cooling chamber Adjust illumination power to real needs Adjust illumination times (movement sensors, door contacts) T8 lamps have a low light emitting efficiency at low temperatures

Reduce waste heat caused by illumination LEDs (E27) can replace incandescent lamps used in deep cooling chambers Ballasts to be installed outside the cooling chamber Adjust illumination power to real needs Adjust illumination times (movement sensors, door contacts) T8 lamps have a low light emitting efficiency at low temperatures Automatic deicing might cause 2-3% higher costs, manual deicing is an alternative

Cooling circuit The lower the temperature at the transfer of cooling energy and The higher the temperature at the transfer of heat The higher is the capacity requirement

Increase evaporation temperature Step 1: Check evaporation temperatures Evaporation temperatures should be as high as possible Step 2: Evaluate design conditions Temperature differences at evaporator

Areas of improvement evaporator Evaporation temperature is too low, caused by unfavourable circulation of air (stapling of goods, moisture in the room) Increase evaporation temperature during nights (3.4K) and during weekends (2.1K) Polluted heat exchanger Deformed fins (proper air circulation in heat exchanger) Iced heat exchanger Fan blads in bad condition, fan does not work Excessive heat at TV or EV

Improve evaporation and condensation temperature Increase the evaporation temperature by 1 Kelvin increases the performance factor up to 3% Decrease the condensation temperature by 1 Kelvin increases the performance factor up to 3 % In case the cooling system has a constant condensation temperature of 40-45°C a variable condensation temperature should be evaluated

Variable condensation temperature

Example: Variable condensation temperature

Recommended condensator temperatures

Optimise condensation temperature Measure the actual condensation temperature or use the temperature indicated in the saturation vapor pressure curve Preasure can be measured between compressor relay and expansion valve

Automatic deicing Automatic deicing might cause 2-3% higher costs, manual deicing is an alternative

Leaks Monitor yearly top-up quantity Calculate indicator: yearly top up quantity/total refrigerant quantity in % Benchmark max. < 20%

Optimisation

Optimisation

Example quick-freeze fruits and vegetables to – 40 °C and storage the final products at – 21 °C. Operating figures per product: Before: 750 kWh/t Afterwards: 200 kWh/t. (European standard) 1.875 MWh/a 500 MWh/a Product: 2.500 t /a Energy needs: 500 MWh Operating time: 960 h/a 2 new chillers á 265 [(2x265)]kW = 530 kW Investment costs: 210.000 € (European standard) Savings per year: 1,3 GWh Savings per year: 54.000 €/a Pay-back period: 4 years