Energy Conservation

Energy Conservation in the Commercial Sector

Jan Viegand, Copenhagen Environment and Energy Office.

The commercial sector is harder to cover for the energy offices compared to private homes. It needs more technical knowledge, and expensive measuring instruments are in general required. It is also natural for a company to make use of a consulting engineering company or the power utility, if the company wants to do something on its energy consumption.

Furthermore the energy adviser must have a licence from the Danish Energy Agency, to be permitted to carry out energy audits that qualify for repayment of CO2-tax. And for many companies the possible repayment will be the motive for having an energy audit done.

But the energy office can take part as initiator targeting all local companies. The knowledge of neighbouring companies, combined with a basic knowledge on conservation potentials, can make the companies decide to have an energy audit.

In addition many energy advisers have sufficient knowledge to advise offices, shops, and small-scale companies on possible energy savings from light, heat, ventilation, office machines, and small refrigerating plants.

The contact to the company ought to happen at the highest possible level. If activities are initiated at the lower level, the management may restrain them. The opposite is very seldom the case.

Company Character and Economy

The energy use is very dependent on the character of the company. Typically the demands are

Most companies can get the energy tax and VAT on purchased energy repaid. However the companies pay half of the CO2-tax from January 1993, unless the energy consumption is very big. The real energy price for the companies can be half as big as the private consumers' energy price.

The low energy price gives the conservation measures a longer pay back period. And into the bargain the companies usually make severe demands on the pay back period: Over three to four years are seldom accepted.

Even if the rentability of a conservation measure is acceptable, there is a high risk that it will not be implemented. The main aim of a company is to produce goods or deliver services, and the resources of the company in terms of staff and capital are therefore reserved for these purposes. The energy consumption has low priority.

The arguments for energy savings targeting the company are:

Working reliability is often the best argument, because production stops as a rule are expensive.

The Energy Audit

An energy audit consists in giving the company proposals for energy savings and their rentability. This can be done at many levels, ranging from a quick examination of the company, and a talk with the staff, to a thorough analysis during several weeks' and use of meters The accuracy of the measures rely of course on the time spent. It depends on the consumption size, how much time it is allowed to use on the energy audit.

The energy audit consists of:

The company seldom knows how much energy is spent on each device. The first important step therefore is to estimate a division of consumption on use. For example how much energy is used for light, ventilation, air compressors, and refrigeration plants. The division can also be made on different sections or places of the production.

The division of the electricity consumption is done by examining the effect of the devices and the service time. A wattmeter gives the effect, and the staff can usually tell, how many hours a day the device is in service. It is difficult to get precise figures, unless measuring over a period.

The important thing about dividing the energy consumption on use, is to find the large consumers and the potential savings.

Next step is to evaluate how the energy consumption is, compared to other similar companies, or compared to the theoretical optimum. The energy consumption shall be related to the output, e.g. as watt light per mě, kWh per produced litre of beer, or kg frozen vegetables. The consumption shall be compared to similar key-figures from other companies in the same line. In the literature list there are mentioned some books with key-figures. As an alternative it must be attempted to get an estimation of the energy consumption from other companies.

Furthermore a comparison with the theoretical energy consumption ought to be done. For a drying installation it can for example be calculated, how much energy is needed to evaporate the water from one humidity to another, in case of no loss.

In this way, it can be discovered, if the energy consumption of the company is higher or dower than the average, and if there are some pans of the production that have a high consumption.

During this first evaluation there can be identified fields which have large savings potentials.

The evaluation is supplemented with a more careful examination of the installations, and any measurements:

The possibilities are described in details under the individual consumption types.

The savings proposals can be here-and-now measures. Or it can be measures which only are economical, if they are done together with other reconstruction or replacement of the installation.

Concerning each proposal the energy adviser estimates the energy saving, other savings for example reduced water consumption, investment, and any change in running costs.

The rentability of the investment is calculated. Preferably both the present worth and the simple pay back period. It is most correct to use the present worth method, where all present and future receipts and expenditures are referred to the present. The method both tells, if the investment is profitable, and which investment gives the highest profit. The advantage by calculating the simple pay back period is that it reflects, when the saving will be. It is also easier to understand.

All calculations on distribution of energy consumption and saving measures are collected in a short report. When the company has studied it, more details can be presented at a meeting. The company ought to be contacted after some time, to hear, if it has carried out the measures.

Energy Management

If the company isn't very interested in the energy consumption beforehand, it should be proposed to start energy control and management, and appoint a staff to be energy manager.

It is important that it is the direction who appoints the energy manager, or at least take the decision to appoint somebody. Else it will be difficult for the energy manager to get proposals through that cost money.

The energy manager shall monitor the development of energy consumption, and come up with proposals that can reduce the consumption. A simple way of monitoring the energy consumption is to make diagrams or curves, where weekly or monthly registrations of energy consumption, and maybe also water consumption, are kept. Computer data sheets can make the registration easier.

The consumption must be compared to an estimated consumption. If an increase in the consumption occurs, due to a fault in the system, then it is possible for the manager to intervene fast, and straighten the fault.

The energy manager calculates the estimated consumption. The first year the estimated figures will not be that precise, but when registration of consumption has taken place for a period, it is much easier to estimate the future consumption. When the company puts a saving measure into work, the calculated saving must be included in the budget. It may be necessary to install more meters, and maybe timers, in order to divide the consumption more.

Type of Consumption and Conservation

Space Heating and Hot Water

Energy consumption related to heating buildings and hot water, can be reduced by the same measures as for dwellings: Afterinsulation, better insulated windows, tightening, lower room temperature, water saving devices, and lower hot water temperature. The possibilities are described more deeply in the previous paragraph on energy conservation in households.

Light

The cheapest advice is, remember to turn off the light when it isn't needed. Especially at work many people forget to turn off the light. It may be in corridors and storerooms, where the staff seldom is, but where the light anyway is on all day. Or in offices, where the light was turned on in cloudy weather, but was not turned off again, when the sun came back.

Even fluorescent tubes must be turned off. Provided one is leaving the room for more than a few minutes, fluorescent tubes must be turned off. The life span is only slightly reduced, and the extra electricity consumption related to keeping the light on, costs far more than changing the tube a little more often.

To be able to turn off, there must be easy access to the switch. And the lighting must be divided, so the light can be off at a window, and on in the middle of the room. If it is not the case, a modification can be proposed, eventually in relation to other alterations of the lighting.

The second cheapest advice is to keep shades clean. It gives no direct energy conservation, but might cause that some of the lamps can be turned off, because the rest provide more light.

Next step is to change the lighting. The easiest way is to substitute incandescent lamps with fluorescent lamps, and old fluorescent tubes with new, thin, and efficient types. There are many types of compact fluorescent lamps, and by trying these out, the best suitable for the lamp is found. Choose electronic lamps, which can stand being switched on and off more often.

Halogenic lamps save a little compared with incandescent lamps, but not as much as fluorescent lamps. One has to realize that halogenic lamps run on low-voltage, and therefore are plugged through a transformer. Even though the lamp is turned off, there is loss from the transformer, which means that it consumes a small amount of electricity all the time. The loss makes the transformer feel warm. Therefore the switch must be turned off, and not only the lamp.

Large fluorescent tubes installations can have electronic precouplings mounted, to substitute the mechanical ones with coils. They have less loss, and because the frequency is higher than the main's frequency, they provide more light. Moreover they last longer. The high frequency technology gives the possibility to subdue the light, either manually, or by a photoelectric cell regulating on solar incidence.

If there are problems with turning off the light, motion detectors, that turn off the light in a room when it is empty, can be installed.

When having a bigger rebuilding the lighting should be evaluated according to the need of light. Danish Standard has recommendations on, how strong the light has to be, related to the task in DS 700, 703, 705 and 707

The distribution between working light and general light in the room must be evaluated. Maybe the general light can be decreased, if there is a good source of light at the working spot.

Holders and lamps with good reflection should be chosen. At last there is the possibility to choose light colours for the walls to reflect light.

By reducing energy consumption for lightening, the heat from light is also reduced. If the offices are ventilated or cooled, the consumption for this also decreases.

Office Appliances

A cheap piece of advice like for the light: Turn off, when not in use. In most offices all computers, printers, photocopiers, telefax machines, etc., are turned on, from the time the first person arrives, till the last one goes home. At larger workplaces some of the appliances are not even turned off before the night watcher makes his round.

Telefax machines have to be turned on day and night, if it shall be possible to receive faxes all the time. Else it might be enough, having it turned on during the day.

Photocopiers are usually used through the whole day, and they must be turned on all the time. Some small photocopiers have no warm-up period, and therefore they are ideal for small demands. They are only fumed on, when a copy is being taken.

Whether the printer can be turned off or not, depends on, if it is connected to one or more users. If there is only one user, it is easy to turn on and off, when printing.

Computers are not damaged by being turned on and off several times a day. Many people turn on the computer when they arrive in the morning, and turn it off when they leave, regardless of it not being used the whole day. Some even have the monitor switched on day and night. It wears the monitor and electronics a little to switch on a computer, but it also wears to have the computer on all the time. And most computers are often replaced by new appliances, before the technical life span is reached.

There may be other small devices in an office, which are coupled to a transformer placed in the plug, like halogenic lamps. It can be an electronic letter balance, a modem, or a charger for a labtop. Even when the device is not in use, there is loss in the transformer, which means it consumes electricity all the time. It is not enough to switch off the appliance itself. Also the switch has to be off.

If it is a problem to remember turning off the appliances, timers that turn off the appliances outside office hours can be installed.

When buying new devices the energy consumption ought to be considered.

Ventilators and Blowers

Ventilation is used for providing a satisfactory indoor climate, and remove unpleasant or toxic substances from a production.

The simplest saving is, only to run the installation, when there is a need. If thermostats, or other automatic, are installed, it must be ensured that they work properly. There can be a need for supplementing the control with timers and motion detectors.

Some ventilation plants can run at variable speeds, and it is therefore possible to choose the performance that fits the need. Moreover exist regulators with infinitely variable regulation of the performance.

Filters on the plant must be cleaned frequently.

Ventilation plants that both draw out air and blow in fresh air, have a heating element to heat the incoming air to avoid draught inconveniences. If it is an electrical heating element, and the room in addition is heated by some other source than electricity, it must be ensured that the thermostat is adjusted as low as possible. One has to find a temperature by experiment, where the staff do not feel draught from the inlet.

If there is no heat exchange between in- and outlet air, the heat consumption can be reduced by a heat exchanger.

The efficiency of the plant might be improved by changing motor, belt drive, or ventilator. It depends on how old the plant is. There can also be some achievement by rebuilding the ventiducts, or other ducts with large drop of pressure.

Blowers are used in production, to move air flows, or products with the air flow. Savings can be obtained by optimum management concerning the demand, cleaning, and replacement of parts with low efficiency.

Pumping

There are pumps in the heating installation, and there might be pumps moving liquids in the production.

At first it must be secured that the pumps are only working, when there is a need.

Second that the efficiency is adjusted to the demand. A valve reduces the volume flux, but does not save electricity. Some pumps have a built-in regulator with variable speeds, where the lowest performance gives lowest electricity consumption. Some pumps have electronic control for infinitely variable regulation. It is possible to mount the control on pumps without a regulator.

If a pump has to work at both low and high performance, it might be an advantage to rebuild, so there are more pumps being coupled in, according to the demand.

Furthermore it must be secured that the size of the pump is adjusted to the plant. By replacing the pump and maybe the engine, if the pump and the engine are not integrated, the efficiency can probably be increased.

If the piping is poorly made, rebuilding might lower the pipe resistance, and thereby the electricity consumption connected to the pump.

Refrigeration

There might be large savings to achieve in relation to refrigeration plants. This counts for plants in both shops and industry.

It must be secured that the plant does not work, when there is no need for refrigeration. This especially counts for freezers, which are only in use during production. Cold stores for storing goods must of course run constantly.

Many refrigerating plants have too low evaporation temperatures and too high condensation temperatures. This leads to high electricity consumption. There must be chosen an evaporator temperature, which isn't lower than the demand. Clean evaporators ensure that enough cold is provided. The condensers must be kept clean as well. The thermostatic control of condenser cooling shall be as low as allowed by the data for the plant.

It is possible to reduce the cooling demand. There might be intrusion of warm air from outside, or there might be heat sources in the room. Maybe the cold store can be better insulated, thus reducing the transmission loss.

There exist various methods to regulate the performance of the refrigeration plant. Improved management can lower consumption.

Some refrigeration plants utilize the condenser heat for space heating or-hot water. This is a good solution, but only if the condenser temperature isn't raised to get hot air or water. Instead it is more profitable to install a heating element for the last heating.

Replacement of motor, and perhaps transmission between motor and compressor, might raise the efficiency.

At last the design of the plant might be bad, which results in too high electricity consumption. This is especially seen, if the original plant has been enlarged to meet a higher refrigeration need.

Compressed Air

Compressed air is used by industry to run tools and valves, etc., and to blow products clean.

It must be ensured that the plant is running only when compressed air is needed. The plant must be adjusted to the needed pressure, and not higher. Cleaning of filters in the installation can lower the pressure loss.

The air drawn in must be as cold as possible, as the electricity consumption decreases, when the air density increases. Therefore it is preferable to draw in air from the open.

There might be many leakages in the piping. By tightening, the compressor performance is decreased, and with this the electricity consumption.

As regarding refrigerator compressors, there are more ways to control them. Changing the regulation might in some cases lower the consumption.

If the air compressor is only used for pneumatic tools, it might be an advantage to scrap the plant, and use electric tools instead.

If there is a heat demand at the factory, it is possible to regain the heat from the compressors.

Engines

Engines are used in industry for running machines, belt conveyers, etc.

It must be ensured that engines are running only when needed. All parts must be regularly cleaned and maintained.

The engine size must fit the demand of the appliance. Often the engine is oversized, causing too high electricity consumption. By alternating need of performance, electronic regulation results in the lowest consumption. It is also possible to have more engines of different size, or one engine which can work at two speeds.

If the engine is low-efficient it might be profitable to change it.

Process heat

Heat can be used for heating, evaporation, drying, melting, etc.

The energy source is electricity or fuels like natural gas, oil, and solid fuel. Energy economic it is in general advantageous to utilize the fuels, as loss at the power plant is avoided. Though electrical heating might be easier to control than fuels.

The process heating must be controlled, so there only is consumption when there is a need.

The demand must be decreased as much as possible, for example by insulation to less heat loss. As we]l as the temperature must be lowered as much as possible.

Concerning drying processes, the consumption can be decreased by removing as much moist as possible before the drying, for example using a hydro extractor.

It might be possible to regain heat from a heated product, and use the heat to preheat a new product.

If fuels are used for heating, the combustion must be with smallest possible loss. Air inlet must be adjusted to maximum efficiency. A poor insulated boiler can lower consumption if insulated.

Literature

Energistyringshandbogen (The Energy Management Handbook). Foreningen for Energistyring.

Handbog i energiradgivning (Handbook in Energy Advisory), eight volumes. Danske Elv'rkers Forening.

Dansk Standard (Danish Standard), DS 700, 703, 705 and 707.