Electrical energy efficiency

Electrical energy efficiency is understood as the reduction in power and energy demands from the electrical system without affecting the normal activities carried out in buildings, industrial plants or any other transformation process.

Additionally, an energy effi cient electrical installation allows the economical and technical optimization. That is, the reduction of technical and economical costs of operation.

In short, a study on energy savings and efficiency will involve three basic points:

• Support the sustainability of the system and the environment by reducing greenhouse emissions as a result of reducing the energy demand.
• Improving of the technical management of the installations by increasing its effi ciency and avoiding stoppages and breakdowns.
• Reduction of the economical cost of the energy as well as the operating costs of the installations.

From a technical point of view, four basic points are considered in order to have a more efficient electrical installation.

• Contract optimizing
• Measurement systems
• Demand management
• Productivity improving by controlling perturbances and costs.

With the four basic points explained, we put forth a series of questions on each point. The questions hope to identify the objectives to work on, in order to obtain an efficient electrical installation.

Contract optimizing

Is your electric contract the most suitable one for your needs?
Do you know that a bad power quality can affects your activities or production processes?

Measurement systems

Do you know how, when and where are you using the electrical energy?
Do you really think that all your energy consumed is the most accurate one?

Demand management

Could you reduce the consumption of electrical energy without affecting the processes or activities carried out?
Would it be possible to improve the technical effi ciency of your electrical installations?

Produtivity improving

Is there anyway to avoid breakdowns and stoppages on your electrical equipment and installations?
Then, could you improve the productivity of your processes?

The first step to do in a process of electrical energy efficiency is to carry out an electrical energy diagnosis and audit. In this process, measurements of power and energy will be taken, as well as other variables necessary for making the suitable decisions.

Along those lines, two key points should be taken into consideration:

• What information do we attempt to get from the measurements?
• Which are the right points to be measured?

In all cases, there are two ways to carry out the audit depending on the installation that is being studied:

Installations that do not have measuring and supervision systems

In this case, measurements must be taken using portable measuring equipment. These equipment permit storing all the variables selected in their memory (power, energy, etc.).

The number of measurements agree with the number of points that are considered to be critical or necessary.

Depending on the type of process, the duration of each measurement will be determined. The aim is to represent the true state of the point measured. The portable equipment permits great fl exibility, but on the other hand, it does not permit the follow up of the energy consumption after the appropriate decisions have been made.

It is recommended to study the points where the measurements are taken for the subsequent installation of a fixed measurement system that communicates with the PowerStudio Scada management software. In this case, the portable measurement equipment is a support equipment used in those places where a fi xed system is not available.

Electrical installations that have PowerStudio management software

In these electrical installations, information can be obtained from the PowerStudio Scada from the data stored in its files.
Then, aside from obtaining information quickly, the critical variables can be followed up.

The incorporation of electronic power equipment is a reality due to the advantages such equipment offers in regards to energy savings and easiness of regulation, that is comfort.

Among these systems, it is worth emphasising all those that regulate or convert some type of electrical magnitude such as UPS, variable speed drives, soft starters, dimmers, PCs, etc.

Along with the energy-related advantages of these systems, their use generates high frequency and harmonic currents, as well as current leakages to ground, thas is a bad waveform quality.

Nonetheless, it is important to distinguish between electric power quality supply and waveform quality. It allows to know the origin of the disturbances.

• The former makes reference to how the utility supply the voltage (interruptions, sags, overvoltages, etc.)
• The latter, waveform quality, makes reference to how the user uses the current, which then affects the voltage. In this case, appear the problems derived from harmonic currents and high frequencies generated by the above mentioned equipment.

As previoulsy stated, besides reducing electric power consumption, an effi cient electrical installation reduces its costs of operation. For a better understanding, each one of these costs is explained in detail hereafter:

Technical costs

What are they
Technical costs are understood to be the loss of capacity in transporation and distribution, as well as heating (electrical losses), disturbances and voltage drops in the electrical installations and systems.

What are they caused by
The following causes are responsible for this technical saturation in the electrical installations:

• Peaks of maximum demand
• Existence of reactive power
• Existence of harmonic currents
• Lines with unbalanced loads
• Use of non effi cient receivers

How are they reduced
Technical costs are reduced as follows:

• Reactive energy compensation
• Harmonic fi ltering
• Phases balancing
• Damping peaks of maximum demand and relocating these consumptions in valley periods

Which are the benefi ts of improving technical costs

• Less energy consumption
• Improved effi ciency in the electric installations by better taking advantage of the distribution lines and transformers
• Decreasing of losses and heating in lines and equipment
• Decreasing of number of breakdowns
• Continuity of electrical service
• Decreasing of the economical costs

Economical costs

What are they
These are the costs of a bill that is not optimized and the amount resulting from the technical costs generated. They can be classifi ed as follows:

• Visible costs
• Hidden costs

1- Visible costs

• These are the costs included in the electricity bill:
• Power contracted not appropriate
• Electricity tariff not appropriate
• Hourly energy consumption
• Demand peaks
• Reactive energy consumption

How are they reduced
By studying the electricity bill, the actions needed to reduce the global cost can be defi ned.

• Adjust the contracted power and change the tariff if necessary. This can be done at almost no cost. Nonetheless, before adjusting the contracted power or tariff, it is recommended to study the processes and the power consumption to see if the demand is adjusted to the real needs
• Eliminating extra charge or cost of reactive energy by its compensation. To do this, a capacitor bank is installed, which in most cases pays for itself within a few months after installation
• Damping the peaks of maximum demand. This consists of not exceeding the maximum allowable power permitted by the utility, and when possible, relocating loads when the energy demand is reduced

2- Hidden costs

What are they
– All unnecessary energy consumption. So, the costs due to unnecessary power and energy consumptions or due to can be dispensable certain time
– All the costs origined as a consequence of the technical costs and the use of receivers that can generate disturbances. Although they are not obvious, they can represent a signifi cant company expense. These are divided into two types:

Electrical installation costs

• Extension of the electrical installations due to:
• Overload of distribution lines
• Overload of transformers
• Losses in distribution due to the Joule effect. This concept is especially important in electric distribution and in industrial plants with long distance lines
• Machine breakdowns (motors, transformers, converters, etc.) and control equipment (computers, PLCs)

Costs in productive processes

• Installation stoppages
• Non-finished product losses
• Additional costs in extra working time and manpower

How are they reduced

• By performing an effi ciency study of the building or industrial plant.
• By correcting the technical costs explained in the previous point.

Which are the benefits of improving visible and hidden economical costs

• Reduced energy consumption
• Decrease of the electricity bill
• No need to invest in the extension of installations due to the lack of capacity
• Productivity improving by reducing the number of breakdowns and stoppages

Ecological costs

What are they
CO2 emissions produced by the consumption of unnecessary energy.
To give an idea of its magnitude, 1 MW·h generated by fossil fuels emits 1 ton of CO2. If considering mixed electric energy generated by fossil fules and renewable energy sources, the ratio is approximately 0.6 tons of CO2 per MW·h.

How are they reduced
By making a general proposal to reduce global energy consumption in an industrial plant or building. So that, an initial diagnosis is required to determine the following points:

• Energy consumption habits
• Current condition of the installation
• Installation of equipment that permits controlling and monitoring the energy consumption in the electric installations
• Energy consumption in each plant or working area
• The energy consumption that can be reduced
• The receivers that can be replaced by effi cient ones

Which are the benefits of improving ecological costs

• Reduction of the emissions of greenhouse effect
• Decrease of technical and economical costs

Legislation

Europa

• Energy Efficiency
• Energy Efficiency Directive
• Buildings
• European Union – Energy
• Research & Innovation
• EU Energy Efficiency Plan

Spain

• Codigo Técnico de la Edificación
• RITE. Reglamento de instalaciones térmicas de los edificios
• Certificación energética de edificios
• Plan de Eficiencia Energética IDAE (E4)