The Smart Grid: Report (2)

This article is part of a series of article about the Smart Grid. It explains the concept of the Smart Grid, how it will evolve and what technologies can/will be used for it. The articles of this series make up a report that I have written for a course that I follow as a student. It is recommended to read this articles in the correct order, because else it will probably be not that easy to understand everything. If there are any comments, remark or such on this report, please do not hesitate to contact me or post it as a comment.

Technology of the smart grid 

Advanced metering infrastructure - Smart meters

Advanced metering infrastructure (AMI) are systems/networks that allow measure, collect and analyse information about energy usage, they retrieve this data from metering devices such as electricity meters, gas meters, heat meters, and water meters, either on request or on a schedule. Then they also can communicate and report on this collected data to homeowners, utilities, and others. These systems include hardware, software, communications, consumer energy displays and controllers, customer associated systems, meter data management software, and supplier business systems.

Smart meters are microprocessor-based devices providing two-way communications capability, and will help homeowners manage their electricity usage. They are the infrastructure that measure the amount of electrical energy used and communicate on this data, possible with the AMI. Through a website, for example, or a customer portal, parameters as to when loads in the home turn on and off based on the price of electricity could be set.

So, the network to which the smart meters and the AMI are connected, are also connected to the smart appliances is the house of the homeowner. But next to that, other elements are connected  to this network, like for example the solar panels on the roof of the house, the electric car in the garage, the ‘smart’ house itself. These elements are explained in more detail in the next sections.

The dishwasher, for instance, could be loaded and set to stand-by until the price of energy is below a certain level – typically off peak – when it would start automatically. In this case the smart meter measures the electricity use of the house and transmits this data to the utilities. The utilities receive this information on the electricity demand of all the households, and so it has a good monitoring system for the flow of electricity in the distribution section of the power grid. With the detailed knowledge about the electricity demand, the utilities can set up a real-time pricing system for the electricity. And using the communication network of the smart grid, it can let the consumers know what the price of electricity is, in real-time of course. The network, is also connected to the appliances in the households, like the dishwasher from the example and so the dishwasher ‘knows’ also the price of electricity in real-time. And that makes it possible to control the dishwasher depending on the real-time price of the electricity.

Demand Side Management - Smart appliances

As electricity demand use grew very rapidly over the last century, the problems of meeting the peak demands grew more challenging and expensive for the utility companies. The backup power that the utilities need to be able to match the electricity demand a peak periods is very costly and makes up a large part of the energy bill.

For a long period of time, most companies instituted a variety of programs to encourage the consumers to reduce their demands at the peak periods. And they achieved in that but only with limited success. Most used method in the past were:

•  Offering cheaper prices during the off peak periods to encourage consumers to switch on their intermediate operating devices during those periods,
•  Offering much cheaper electricity prices to customers who were willing to be shut off during peak demand periods,
•  Providing services to consumers to encourage more efficient electricity use,
•  Encouraging investment in distributed generation sources that would reduce peak demands.

Some of these demand side management method were dropped under the deregulation of the electrical industry, because form that moment on the generation sector became separated from direct interactions with the end consumers on the power grid. New generation companies focused on producing electricity at most competitive rates instead.  

In the concept of the smart grid, smart appliances are supposed to be used to take demand side management to another level. By installing and connecting smart appliances in a household to the smart grid network, utilities can decided, within some limited range, when these smart appliances will be switch on and/or off. In that way it is possible for the utilities to try to match the demand with the supply – especially when there are many renewable energy sources with a variable electricity production connected to the grid. Or on the other hand, by using smart appliances, utilities can avoid peak demands far more than with current schemes where they must convince the user to avoid consumption during the periods of peak demand. (3)

Virtual power plants

A virtual power plant is a cluster of decentralized generation installations, that are controlled from one central point or one control centre. These installation can be micro-CHP, wind turbine, solar panel arrays, small hydro generators, etc. But it is very well possible to add storage capacity to the set of generation installations of a virtual power plant. These small decentralized generation installations achieve the characteristic of a big plant through their combination. For the realisation of a virtual power plant, communicative crosslinking is a critical issue. Like a simple network of personal computers, a virtual power plant links together seldom-used standby and emergency backup generators at hospitals, universities, manufacturers, office towers and other facilities. This network of small power plants allows utilities and high-energy users to draw additional power from these on-site sources as needed.

A virtual power plant, when considered as an additional element to the power grid, can be very useful to prevent outages and improve the reliability of the power grid. The concentrated operational mode delivers extra benefits such as the ability to deliver peak load electricity or load-following  power at short notice.

Microgrids

A microgrid is a localized grouping of electricity generation, energy storage, and loads that normally operates connected to a traditional centralized grid. This single point of common coupling of the microgrid with the centralized grid can, in most cases, be disconnected. In that way, a microgrid must be able to operate entirely autonomously. Generally, the generation installations and the different loads of a microgrid are interconnected at a lower voltage than that of a traditional centralized grid. This is possible because the distance, where over the electric energy must be transported is, in the case of a microgrid, a lot smaller than with a traditional centralized power grid. So, even with lower voltages, the energy losses during the transport of the electric energy are still limited.

From the point of view of the grid operator, if the microgrid is connected to the central grid, it can be operated as if it was one entity. In a fact a microgrid is very similar than a virtual power plant, except from the locations of the generation installations. With a virtual power plant, the placement of the generation installations is dispersed, and as with the microgrid the installations are grouped together to one place.

Distributed generation

Distributed generation, or decentralized generation or on-site generation is the generation of energy by using many different installation that are placed at different location. In general these installation are a lot smaller than the big central generation plants, such as coal-fired plants or nuclear plants. Distributed generation installations are small-scale power generation technologies, typically they can have a power capacity of 3 kW to 10.000 kW. Many of the renewable energy technology, like solar panels and wind turbines, have a capacity that is typically for distributed generation installations and mostly they are placed spread over several different locations. So, renewable energy installations can, in many cases , be seen as a technology that belongs to the group of distributed generation.

Currently, industrial countries generate most of their electrical energy in such large centralised generation plants, mostly coal fired plants. This is because such plants have excellent economies of scale – the cost advantages that a business obtains due to expansion. But coal fired plants have detrimental consequence for the environment and global climate. Distributed generation is a very different approach, their economy of scale isn’t as large as that of coal fired plants and so is their cost of generation larger but their effect on the environment and global climate is in many cases a lot smaller than with coal fired plants. And distributed generation does reduce the amount energy lost in transmitting the electrical energy because the electricity is generated at or near the locations it is being used. And so, this also reduces the size and number of power lines that must be constructed.

Decentralized generation installations are very good candidates to be added to a virtual power plant. They have similar size, power capacity and dispersed placement as the other installations of a virtual power plant. And if they are added the enough other kinds of electricity generation technologies, they can be considered as one entity by the grid operators (3).

Examples of distributed generation technologies are:

• Combined heat and power,
• Fuel cells,
•  Micro combined heat and power,
•  Micro turbines – small gas turbines connected to a generator,
•  Photovoltaic systems,
•  Piston engines,
•  Small wind power installations,
•  Other.

Geschreven door Emile Glorieux