Practical energy conservation - a case study

W. W. WOODBURN The Scottish Milk Marketing Board - Galloway Creamery

The results of an energy conservation programme are described. The project consisted of an initial survey to assess the potential for conservation. the formingof an energy management team, andadoption ofapolicy. More than 20 major projects were tackled, which resulted in a reduction of more than 2Opercent in energy costs.

Galloway Creamery is the largest of the Scottish Milk Marketing Board's six manufacturing creameries, situated at Stranraer, Wig- townshire, in the heart of one ofthe most intensive dairying areas in the United Kingdom. Up to 750,000 litres ofmilk per day are handled during the peak season. and Cheddar cheese, butter, casein, casei- nates, whey powder, demineralized whey powder, and skimmed milk powder are manufactured.

Milk intake, products, and energy and water usage for the years 1979-81 are shown in Table 1. Table 2 shows energy and water costs for 1981. From these statistics it is obvious that energy is a major item in production costs, and it was in our efforts to control these costsand to identify ways in which energy could be saved that the Scottish Milk Marketing Board sought professional advice from P.A. Management Consultants during the spring of 1979.

These consultants carried out an investigation into the use of energy at Galloway Creamery with three main objectives: 1 to make a broad assessment ofthe scope for reducing energy costs

and the time-scales within which these reductions should be possible;

2 to establish priority areas for attention; and 3 to determine the most suitable approach to reducing energy costs

at Galloway.

TABLE I Galloway C'reamery: Intake. production,

energy and water statisfics 1979-81

1979 1980 1981

Inlake Milk and skimmed milk intake (kl) t'roduc/ion (k tonnes) Cheese Cnseinlcaseinate Butter Skimmed milk/whey powder Eneqylwa~er Electricity (kWh) Oil (litres) Water (k litres) Electricity (kWh/1000 litres) Oil (litres/lOOO litres) Water (1000 litres/1000 litres)

108,225

4,182

3.687

5,497,980 4a6.660

1,339 2.599

6,104,300

56.3 50.7

4.5

9 1,463

4.143 1,144 1,976 2,439

4,264.5ao 3,560.593

33 1.875 46.6

3.6 38.9

114,424

4,70 I 1,109 2,896 3.938

361,608

4,712,510 4,243,509

41.2 37.1 3.2

TABLE 2 Galloway C'reamery: Energy and water costs 1981

~

Electricity 4,712,510 kWh at 3 . 3 ~ = €155,513 Fuel oil 4.243.509 litres at 10.98~ = W65.937 Water 361.608 ni3 at 1 0 . 2 4 ~ = ~37,028

Total 5658,478

The principal conclusions arising from this investigation were: Energy costs were approaching €0.5 million per annum. Scope for energy reduction was identified, in financial terms, in the range €40,000-€60,000 per year. It was also anticipated that some of this could be achieved without capital expenditure ar?d much without significant expenditure. Some specialist consultant assistance was considered necessary to: (a) establish energy cost recuction as a formal and continuing

(b)spearhead the attack on energy costs and set in hand an

(c) ensure that potential savings were optimized; and (d) ensure that the time-scale for achievement was minimized. Up to 50 per cent of consultancy fees could be funded by the De- partment of Energy under the Energy Survey Scheme.

responsibility;

energy cost reduction programme;

After considering the results of the investigation the Scottish Milk Marketing Board decided to start an energy conservation programme with P.A. Consultants involvement to assist management at the Galloway Creamery.

ENERGY MANAGEMENT TEAM The first step was to form an energy management team in order to: 1 prepare the strategy and overall plan ofaction for reducing costs; 2 create an atmosphere in which all personnel would contribute to-

wards energy savings; 3 prepare statistics in order to show weekly energy efficiencies in re-

lation to the product handled, which would highlight problem areas, help to create targets, and allow the calculation of energy cost per tonne of cheese, butter, etc;

4 provide technical support where this was required. The energy team consisted of the group manager, production man- ager, departmental assistant managers, engineering and electrical foremen, and a P.A. Consultant.

ENERGY AUDIT An energy audit is the detailed measurement ofall energy used, which highlights the areas of major usage. The next step was to start record- ing the following information.

Record department electricity consumption in order to establish: electric units/tonne of cheese manuhctured; electric units/tonne of butter manufactured; electric units/1,000 litres milk intake.

Calculate boiler efficiencies, using oil consumed and feedwater into the boiler. Record water consumption by boilers and for general purposes in the Creamery. Start enquiries regarding the most suitable type of steam meters for the Creamery. Oil for steam raising was the major contributor to the energy bill, and therefore it was desirable to monitor steam consumption in each department to highlight the areas where waste occurred. This would also show:

kilograms stearnhome of cheese produced kilograms steam/tonne of butter produced kilograms steam/tonne of powder produced

96 Journal of the Society of Dairy Technology. Val. 35, No. 3, July 1982

STAFF AWARENESS OF ENERGY USAGE When the conservation plan had been formulated, it was decided that all staff at the Creamery must be informed ofthe intentions for energy saving. Everyone on the site was made aware ofthe cost ofenergyand ofwhat steps should be taken to save it. A seriesofshortapppreciation courses emphasized areas of wastage that could be eliminated, there- by reducing the energy bill, so that the present level of staffing could be maintained during the time of lower milk intake, especially when all costs werecontinua1lyrising.Targetswerepinned toall notice boards, and results achieved were made known to all staff. Films were shown, highlighting the role personnel could play and communicating to them the cost of: (a) a water hose left running; (b) a motor left running; (c) lights left on; (d) compressed air leaks; and (e) steam leaks. These courses helped to create an atmosphere and attitude which encouraged departments to identify their own potential energy-saving projects.

GOOD HOUSEKEEPING Many technical methods to conserve energyare very costly. However, many aspects require far less technical consideration which any dairy engineer can implement easily. These are general good housekeeping measures.

Basically, energy conservation is the commonsense and respon- sible use of steam, electricity, water, air, etc. Proper lagging of steam pipes, condensate pipes, chilled water pipes, etc., making sure steam traps are working efficiently, switching off equipment not actually in use, and controlling lighting all contribute to energy savings.

Lagging pipes Unlagged pipework, whether in process or space heating, inside or outside, will dissipate excessive amounts of heat. This puts an extra unnecessary load on the boiler plant and increases costs. Consider, for example, a 10-metre length of steam pipe, 3 inches in diameter, carry- ing steam at 100 psi and operating 24 hours a day. Unlagged, the an- nual heat loss at 1981 prices will be equivalent to a financial loss of €705, which is reduced to E66 if the pipe is lagged, apotential saving of E639/year. The cost of the lagging will be recovered in 0.2 years.

At Galloway €12,000 was spent on additional lagging for steam pipes, flanges, valves, condensate pipes, etc, to give an estimated an- nual saving of €22,500.

Steam leaks These can be divided into two categories, detectable and undetec- table. Detectable leaks occur at valves and flanges, pipe joints, etc. They are usually detected very easily and can be repaired before the leak becomes serious. Undetectable leaks result from faulty steam traps, worn boiler blow down valves, and faulty safety relief valves. These leaks are not detected easily, because the leakage passes into condensate return pipes or is vented to drains.

At Galloway€2,000 was spent replacing existing steam traps to pro- duce savings off10,OOO per annum. Weekly checks on all steam traps are made using an ultrasonic detector in order to maintain these savings.

General hosing

It was decided to reduce the temperature of hosing water from amaxi- mumof70uC to55aC.Thisgaveasavingof37.8 thermsaday, whichat 35pAherm gave a financial saving off13.25 or €4,630 in an operating year of 350 days.

Hose size was also reduced from 0.75 to 0.5 inch, giving a saving of 20 per cent in water used and consequently an additional saving of 20.2 thermdday, a financial saving of €2,474 in an operating year of 350 days.

PROJECTS As well as introducing good housekeeping techniques within the Creamery, it appeared essential that the energy management team should implement alist ofprojects for all to discuss. Eachone ofthese

projects was then allocated for implementation to a member of the energy team. A list ofthe projects implemented, along with the capital cost of the projects and savings made, follows:

Capital Annual costs (€) savings (€)

Power factor correction Purchase of 4 - SO kva capacitors to bring power factor as near to unity as possible

Fuel heating (new boilers) Fuel oil in tanks heated by steam during production hours

Fuel heating (old boilers) Fuel oil in tanks heated by steam during production hours

Lagging steam pipes, condensate pipes. etc. Lagging of all steam pipes not already lagged, replacing old lagging, covering flanges and steam valves, etc.

Steam traps Replacing existing steam traps with bimetallic traps and also membrane- type steam traps

Blowdown heat recovey Installation of a Gestra automatic boiler blow-down system with a heat recovery unit to heat boiler feedwater

Electrical housekeeping controls After the installation of additional electric meters, each department could be monitored from day to day and week to week

Boiler eflciency

No saving estimated, because tests on two boilers showed that they were efficient

Chilled water Use of chilled water was reduced by replacing mains water supply to some areas: (a) cheese starter cooling. saving

(b) cream pasteurizer, saving MOOlyear

€9,400/year

Casein wash water Warmed mains water from the cream pasteurizer was piped to a storage tank and then quickly used as wash water for the casein plant. This replaced cold mains water, which was used at the rate of 3,000 gal/h to wash the casein curd.

Casein throughput

Initial experiments to reduce energy usage, included lagging air heater banks more efficiently and carrying out more mechanical drying. But it was eventually decided to increase the casein throughput instead. A 2Wa increase in throughput resulted in the same production with less shift working.

Condensate return Extra condensate was piped to boilers, providing lW/o of the feed water requirement instead of 5@/0 as formerly. Feedwater temperature to boilers was raised from 52OC to 68OC leading to a 2.5% saving in fuel.

2,800 1,400

Nil 3,600

350 1,200

12,000 22,500

2.000 10,000

8,400 6,000

1.000 7.000

2’ooo e s t z i t e d

1,000 10,OoO

1,000 4,000

600 6,500

Journal of the Society of Dairy Technology, Vol. 35. No. 3, July 1982 97

Capital Annual costs (€) savings (f)

Not applicable

Capital Annual costs (&) savings (f)

Nil 1 .(NO New compressor A new air compressor was installed, and the heat produced from the compressor was rejected in the form of warm air to heat the powder store, giving excellent storage conditions.

Boiler scheduling A written schedule for the engineers, specifying the start-up times for the major items of plant, was made out each evening. This eliminated running too many boilers and unnecessary early start-up. Savings were estimated at Ph of fuel.

Maximum electrical demand Maximum electrical demand in the factory was controlled manually by switching off sheddable loads such as butter and cheese cold store cooling during periods of peak demand. Saving is 165 kva each month, 165 x f1.98 x 12 = E3.920.

Lighring After a lighting survey carried out in the Creamery, new recommendations were implemented Lighting removed - 3.2kW Lighting installed - 1.8kW Saving €140

Lagging chilled water pipes Extra lagging was added to the chilled water pipes servicing the Creamery.

Delayed evaporaror start-up This project came under the General Good Housekeeping heading, where evaporators were not started up until the last moment. Saving: 0.5 hour x f50/h x 300

days = €7,500.

Warer-softening plant installation A water-softening plant was installed to produce de-ionized water for the demineralization plant. This saved 3 hours per day evaporator running time for 100 days. Saving: 300 hours x SO/h = €15.000

Compressed air leaks All air leaks were attended to instantly. The saving made wdS estimated at €1.000.

Steam housekeepinglcontrols Two types of steam meters have been installed, but both were

Nil 7,000 unsatisfactory and have been removed from site. Any capital expenditure has been recouped by the Creamery.

Total

Nil 4,000

200 140

51,700 125,000

It has been decided as a result ofour efforts that it is important that we continue to investigate energy conservation by evaluating new projects and monitoring energy usage. The projects currently under scrutiny (some in fact have already been given the go-ahead) are:

1 Boiler draught control, i.e., air tight burners 2 Automatic cold-store door. 3 Use of warm air at top of spray-drier building for intake air. 4 Pre-heating of air for boilers. 5 Plastic strip curtains for store doors and sides of fluid bed drier. 6 Insulation at garage, cheese stores, and butter chill. 7 Pre-heaters for spray-drier air intake using evaporator condensate. 8 Cavity wall insulation for butter store and of ice block. 9 Heating of powder store.

10 Recovery of waste heat from refrigeration process.

450 450

Nil 7,500

CONCLUSION The case history of Galloway Creamery shows that the benefits achieved during the course of the energy conservation project have been substantial, and the savings attributable to energy alone were in the order of €120,000 for 1980. This amount was almost double the original projection and supported the decision made to begin this pro- ject. It is important that support from management and all staff is obtained to ensure success.

3,000 15,000

98 Journal of the Society of Dairy Technology, Vol. 35, No. 3, Julv 1982