Progress took a giant leap forward when our ancestors imitated lightning bolts to start the fires they used for heating, lighting, cooking and conviviality.
Electricity now powers the modern society, whether turning on and off tiny microprocessor switches millions of times a second or sending locomotives hurtling along the track at over 500 kilometres an hour.
Here we will learn more about the way today’s electricity is generated and delivered. We’ll also look at the growing need for electricity, the challenges this poses for the electrical grid and how these challenges are being addressed.
What is electricity?
The basics
So what is electricity exactly? Usually, we’re talking about different things at the same time. Naturally occurring electricity is called electrical charge. It is a fundamental property of matter, carried by several elementary particles.
Generated electricity is electrical or electromagnetic energy. It flows at almost the speed of light and is measured in Watts. A source such as a battery or generator put sit into a circuit, where a “load” such as alight bulb consumes it and so removes it from the circuit.
Electric power
Electric current refers to electrons flowing along a wire or other conductor. The rate of this flow is measured in amperes (A), and is based on the number of electrons flowing past a given point in a second.
The force that drives the electrons in the wire is called the voltage. It is similar to the pressure that drives water in a pipe and is measured in volts (V).
Electrical power is proportional to the voltage multiplied by the current. The wire used to transmit the power does not allow all the current to pass through it unimpeded. There is a resistance, similar to friction, which causes the wires to heat and energy is lost.
Since the goal of transmission is to get a given amount of power from A to B, these losses have to be reduced. A law of physics states that as voltage is increased, proportionately less current is needed to transmit the same amount of power. Increasing the voltage by a factor of 10 reduces the current needed to transmit the same power by a factor of 10, and thus the energy lost to resistance is reduced by a factor of 100.
Key dates in history
600 BC Discovery of static electricity
1600 William Gilbert invented the term electricity
1750s Benjamin Franklin proved that lightning is a form of electricity
1800 Humphry Davy discovered Electrolysis
1820s Thomas Johann Seebeck discovered thermo electricity
1830s Michael Faraday establishes the principles of electricity and magnetism, known today as “field theory”
1870s Thomas Edison built a DC electric generator
1880s The first public electricity supply
1920s First National Grid was introduced in the UK
1950s First large-scale nuclear power station opened
2000 The world’s first commercial wave power station began to generate electricity
How much electricity do we use?
Electricity consumption is measured (and billed) in Watt hours. If left on for an hour, a heater rated at 1,000 Watts (1 kW) consumes 1 kWh. Global electricity generation is now over 20,000 million million Watt-hours or terawatt hours (TWh). This is expected to rise to over 27,000 TWh in 2020, and to 35,200 TWh in 2035. More than 80% of growth in electricity demand will be in non-OECD* countries, whose consumption will triple by 2035.
Who uses electricity?
At over 7,000 TWh a year, industry is the world’s biggest user of electricity, followed by residential use (4,600 TWh) and commercial and public services (4,000 TWh).
Per capita use varies enormously from one country to another, ranging from over 36,000 kWh in Iceland to only 9 kWh in Chad.
How vital is electricity?
Electricity is an “enabling” technology, allowing most of the other technologies we use to work. Today’s economy couldn’t function without the electricity used to power factories, light offices and shops, power communication networks and drive thousands of different appliances.
How is electricity generated & delivered to customers?
Except for photovoltaics, electricity is still generated using principles developed by Michael Faraday in the 1820s and 1830s. Copper wire wrapped around a shaft, or armature, is spun in a magnetic field. The motion of the magnetic field relative to the copper wire causes electrons to flow in the wire, creating electricity. Different technologies and fuels are used to power the machines that spin the wire.
● Coal-fired power stations produce 41% of the world’s electricity at present, with natural gas producing 21%, hydro 16%, nuclear 14% and oil-fired generation 5%.
● N on-hydro renewables like solar and wind power are our fastest-growing energy sources. They only account for around 3% of generation today, but their share is projected to rise spectacularly to 16% by 2035, mainly at the expense of coal, whose share drops to 32%.
It is possible to store electricity, but even the latest battery technology is not efficient enough to stock the power needed for all our daily consumption.(other option is pumped storage hydro plants)
Once electricity is generated, it is transmitted at 300,000 km/sec. The network of lines used to do this is the grid, or high voltage transmission network.
High voltage current is too powerful to be used directly. A system of medium voltage and low voltage networks delivers electricity to utility companies for distribution to end users, or to large industrial clients who have their own installations for transforming it to usable levels. The overhead lines of the distribution network are the most visible part of power supply systems. Medium voltage networks (usually 10 to 30 kV) supply urban and rural areas. Low voltage networks supply 220-230 V or 110 V electricity locally to households and small industries nearby.
What are electrical grids?
The electricity generation, transmission, distribution and control networks make up the electrical grid. The simplest grids link a local generator to homes, but grids can cover whole continents too. Smaller grids have a radial structure with supply lines branching out from a large centralised electricity supplier. This is relatively simple to operate, but if a line goes down, users are cut off.
To ensure reliable supply, most grids use a mesh structure. In this configuration, the power lines of any given electricity supply source are interconnected with those of other sources. If one line has a problem, power can be rerouted from elsewhere while the damaged line is repaired.
To plan, operate and manage large interlinked systems, we need control centres where operators monitor grid status. They will adjust to electrical demand variations in real time, using sophisticated network management systems.
The AC electrical grids are composed of substations connected to each other by overhead, underground, or even submarine lines.
In connecting larger networks across countries or continents, we are facing a challenge: directly connecting AC grids with different frequencies is not possible. DC is the answer. We therefore convert AC into DC to enable the interconnection.
Did you know? In order to reduce losses, the electricity generated by the power station (in the range of 10-20 kV) is first stepped up to 230 kV or 400 kV in Europe, 500 kV in the Americas (except Canada where up to 765 kV is used) and as high as 1,100 kV in China. It is then transmitted by high voltage transmission grids at powers of up to 800 kV. From the grid, the electricity is converted by transformers in the distribution network, stepping the power down to medium voltages (below 50 kV) and finally to the voltage used by consumers (220-240 V in Europe or 110 V in North America).
What is an electric substation?
Substations are a familiar sight alongside highways and in cities. Substations take the electricity from power plants and from the transmission lines and transform it from high to lower voltage. They distribute electricity to consumers and supervise and protect the distribution network to keep it working safely and efficiently, for example by using circuitbreakers (the industrial strength equivalent of the humble fuse) to cut power in case of a problem.
Substations are often classed according to the switchgear used to protect their circuits.
● Air-insulated switchgear (AIS ) used to be the most common design, but this requires a lot of space and for higher voltages is only feasible outdoors. Even then, AIS may be unsuitable or undesirable in certain locations, such as residential areas.
● Gas-insulated switchgear (GIS ) may be more expensive if only the unit cost is compared, but is safer and needs less maintenance. The fact that GIS units are five times smaller than AIS means cost savings and smaller, less intrusive buildings.
Electrical lines can be overhead or underground. The construction of overhead lines costs less, but outages are more common than on underground lines (due to bad weather, lightning strikes or accidents).
What do we find in a substation? Power transformers, switching devices such as circuit breakers and disconnectors to cut power in case of a problem, and measurement, protection and control devices needed to ensure its safe and efficient operation.
AC or DC?
DC or AC? The high voltage transmission system can be high voltage AC (HVAC) or high voltage DC (HVDC). In a direct current (DC) system, the electrons flow in only one direction (“forward”), from the negative to the positive terminal marked on a battery for instance.
DC is more efficient when transmitting large amounts of power over long distances, and when using energy sources remote from load centres.
In alternating current (AC) the electrons flow forwards and backwards alternatively. One trip forwards and back is a cycle, measured in cycles per second or Hertz (Hz). In AC systems, significant amounts of electrical energy are lost because the conductor heats up( Rac>Rdc, 1.4 times)
Why do we have two types of current?
Thomas Edison’s company was producing electricity in 121 power stations by 1887, using the DC system. One advantage of DC is that the voltage, the electrical force needed to drive current between two points, is fixed.
This is useful for applications that need an unvarying supply, such as electric railways. However, at the time, Edison’s DC system could only supply customers within about 2.5 km of the plant.
Thomas Edison’s great rival was George Westinghouse and his AC system. With AC, Westinghouse was capable of transmitting current over hundreds of kilometres, and soon won the “war of currents”. That is why today, AC remains the standard for electric power.
DC technology has improved spectacularly since Edison’s time. Modern DC systems can transmit five times more megawatts across the same pylons and lines, making DC increasingly attractive to grid operators and industry. Moreover, HVDC dramatically improves power flow reliability and stability
Challenges of electrical grids
Growing power demand
A combination of growing demand for electricity and the need to upgrade or replace existing equipment means that massive investment will be required to meet future needs. The International Energy Agency estimates that over $6 trillion needs to be invested in transmission and distribution by 2030, and as much again on generation. A total of 5,087 GW of generating capacity will be built worldwide by 2030, with 2,700 GW of that in developing countries (1,100 GW in China alone).
Distance of power transmission
Electric power is often generated in plants far from users, and near to coal, gas, hydro or other inputs. Covering the distances between producer and consumer is the first challenge of transmitting electricity. With less loss due to resistance, the longest distance lines are HVDC - well suited for long distance transmission from point to point.
HVDC is the only way to interconnect two asynchronous AC systems. HVDC is the answer: move more power, more efficiently, with the lowest losses possible.
Integrating renewables
One problem with increasing the use of renewable energy sources is that inputs can vary considerably. The sun can stop shining, the wind can drop with little warning and a dry season can reduce the flow to hydroelectric plants. Even too much wind can be a drawback if it blows at night when there is little or no demand for the energy generated. Solutions must consider how to integrate different sources seamlessly into a single network to supply power cheaply, safely and dependably. Advanced software will help power suppliers to anticipate demand fluctuations. Developing storage devices that can hold more charge will allow electricity to be stocked.
Efficient power supply
Around two-thirds of primary energy is lost, mainly due to power conversion, and up to 16% of electricity generated never reaches users – it is lost by the networks, like water leaking from a pipe. The US Energy Information Administration calculated that electricity lost in transmission and distribution cost the economy $20 billion in 2005. Using modern HVDC technology to manage connections among the different parts of the system (energy conversion, energy storage, control and power transmission) could help to produce savings by preventing outages and reducing the space needed to house equipment.
Building new equipment is one way to try to meet the growing electricity demand, but improving power supply efficiency could allow us to do more with less.
Power supply reliability and stability
Reliable electricity supplies are vital for activities like hospitals or air traffic control, while industries like steelmaking depend on large amounts of power to function. Transmission operators use a number of techniques to improve grid reliability, such as real-time control and monitoring systems to acquire information on the state of the network and make power available on demand.
An HVDC link is often used to connect AC networks, with transformers at both ends to match local input or output requirements. HVDC dramatically improves power flow controllability and acts as a firewall by stopping the propagation of faults that could cascade through a network.
Compatibility and standardisation
Travellers know that adapters and transformers are required to make sure appliances can be operated in different countries.
The same problems occur on a vaster scale with transmission networks. They complicate the already difficult task of interconnecting systems between countries or across continents. One solution to overcome this is HVDC.
The lack of standardisation also means that the different power systems cannot communicate with each other, plus equipment from different manufacturers cannot always function properly together. Great efforts are being made to rationalise communications and guarantee interoperability between equipment. The IEC 61850 substation communication standard (high-speed communication of digital information between devices) is one good example.
Increased distributed energy resources
Electricity consumers are becoming increasingly proactive. They like to actively control their electricity use and bill, shifting their consumption in real-time to the most favourable tarif.
It is also possible for consumers to sell power to utilities from their own solar panels, wind turbines or other installations, or they may choose to store it for electric vehicles and other uses.
Integrating these distributed energy resources means moving beyond the traditional centralised structure to a highly dynamic grid, where the electrical network is intertwined with information and telecommunication flows.
Deregulation
In deregulated electricity markets, the price of electricity can fluctuate widely by the hour or even by the minute. Until recently, electricity consumers did not receive relevant information in real-time and typically paid a flat rate.
The deregulation of electricity markets and the increase of consumer level technology, such as smart meters and demand response, will lead to more proactive behaviour from the endconsumers.
As customers evolve to exploit the possibilities of demand management, they will soon be able to install small-scale distributed generation at home and sell the electricity. With such benefits, deregulation will continue and increase.
Meeting the challenges
A smart, direct future
The 21st century will see DC coming back into favour. Modern DC systems can transmit up to five times more power across the same pylons and lines as AC systems. Given the increasing difficulties in obtaining permission for power lines in both urban and rural areas, HVDC may be the only solution for increasing capacity.
Smart Grid
When most people think of a network these days, they think of the Internet or phones. The communications revolution wouldn’t have happened if you still had to call an operator before getting connected to another person.
Likewise, tomorrow’s electricity network will have to be smarter, as it faces new demands. In particular, some of the challenges presented earlier require a transformation of electricity infrastructures towards Smart Grids in the next decade.
● Countries are trying to improve the energy efficiency in their grids, to support their booming markets or better respond to their citizens’ electricity consumption.
● Grid operators worldwide aim at achieving higher reliability for their networks to prevent blackouts.
● Integrating new renewable energies is becoming a priority with the increased importance of the fight against CO2 emissions.
Electricity networks have started responding to these challenges. They now increasingly integrate new information technologies, communication systems and power electronics.
The Smart Grid represents the evolution of the traditional electricity network: it is a new generation energy transmission and distribution network integrating advanced control, IT , telecommunications and powerelectronics technologies. It provides a real-time, two-way flow of energy and information across the entire electrical grid, from the power plant to the house of the individual consumer.
The Smart Grid secures and optimises the electricity flow across its entire journey. So, the grid is becoming fully dynamic, and electricity management is entering a new era, with unprecedented efficiency and stability.
As a pioneer and global leader in its field, Alstom Grid is committed to meeting these challenges, helping to shape the future of our electrical grids.
Did you know...
Most electrical accidents are due to defective equipment, unsafe installation, or misuse, and can be prevented by following a few basic electricity safety rules:
● Make sure you use certified suppliers and electricians
● Avoid overloading power outlets with too many appliances
● Unplug appliances when not in use
● Protect electric cables
● Follow specified safety advice at all times
One lightning bolt has enough electricity to service 200,000 homes. In one hour, the Earth receives more energy from the Sun than total world energy consumption for a year.
Switching to the best technologies available today would save at least 40% of residential electricity consumption in most appliance categories.
Standby power accounts for 10% of residential energy use in the OECD area. In other words, devices doing nothing add 10% to the average electricity bill.
The Greek philosopher Thales of Miletus unknowingly experimented with static electricity in 600 BC. He rubbed amber (elektron in Greek) with cat fur and picked up feathers. He thought the attraction was due to magnetism but in 1600, English scientist William Gilbert showed that magnetism and static electricity – that he called “electricus”, meaning amber-like – were different.
Obama’s Smart Grid Plan: On 27 October 2009, the Obama Administration announced an investment totaling $3.4 billion, for supporting Smart Grid efforts.
The terms we use to describe electricity are tributes to pioneers such as Volta who invented the electrochemical battery, Ampère and Hertz who worked on electromagnetism, Watt who developed the concept of horsepower, or Ohm whose law defines the relationship between voltage and current.
Sources
International Energy Agency
World Energy Outlook www.worldenergyoutlook.org
US Energy Information Administration www.eia.gov
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