Proponents of renewables, such as wind and solar, like to compare the grid with the Internet. The analogy attempts to establish that the grid and Internet are similar, and that adding renewables to the grid is no more difficult than adding a computer to the Internet.
The grid and the Internet, however, are fundamentally different.
While it’s easy to connect large numbers of electronic devices, such as computers or I-phones, to the Internet, it’s an entirely different matter to connect large numbers of renewable generating equipment to the grid.
The difference can be summarized with one word: Power.
Internet devices operate on very low voltages and current, while the grid operates on very high voltages and currents.
Basic electrical engineering may be similar, but there is a huge difference between power engineering and engineering involving electronics.
In the world of power engineering, Power=V*I*Cos θ.
High school physics students will probably recognize this basic formula.
Grid voltages can range from 110 to over 500,000 volts. Cos θ is the phase angle due to impedance caused by such things as motors or capacitors. An angle that varies from 0 degrees, results in wattless energy, which, simply stated, is electricity produced by a generator that doesn’t reach the user.
Transmission and distribution is done using three phases, while the electricity that enters a home is single phase.
Most people are only concerned with single phase AC electricity that enters the home, but the grid operator must work with the three phases from multiple sources. For example, the frequency of electricity from two different sources must be precisely the same and be in-phase with a very small tolerance for error, or huge destructive forces will be unleashed: Forces so strong that they can destroy equipment.
The wall switch in a home or office, at 110 volts, can interrupt the flow of current without creating an arc. But, a circuit breaker in a substation, where voltages range from 7,000 to 100,000 volts or more, must have special quenching devices to interrupt the arc. Without the ability to quench the arc there would be serious damage to equipment, including the probability of an explosion and fire that would bring down that portion of the grid.
This quick dissertation on the forces involved with the grid, is to compare them with the virtual lack of electrical forces found on the Internet.
Powering a bit, or a packet containing bits or bytes, on the Internet requires very little power1.
Voltages are around 5 volts, while current is DC, usually at far less than 1 amp. The resulting power is miniscule compared with power found on the grid. Power on the grid is sufficient to do work, or create immense destructive forces, while power on the Internet is only capable of pushing bits or packets along coaxial or fiber optic cables. Individual components on the Internet may have somewhat higher currents, but their power ratings in watts, are still miniscule compared to the power found on the grid.
Comparing the grid with the Internet is grossly misleading.
Laying coaxial cable or fiber optic cable, together with their relays, is easy compared to building transmission or distribution lines with their transformers, circuit breakers and other related equipment.
Controlling packets on the Internet is simple, compared with controlling the flow of electricity from multiple sources on the grid.
Routers on the Internet are small, both in rating2 and physical size, compared with equipment found on the grid.
The internet can operate at various levels of usage, while the grid must constantly maintain supplies that equal demand. Let supply and demand become unbalanced, and the grid, or portions of it, shut down.
Wind turbines, PV solar and concentrating solar are intermittent sources that complicate operation of the grid, such as maintaining the balance between supply and demand.
Renewable generation equipment added to the grid creates a multitude of problems, such as frequency regulation, sudden changes in load and maintaining voltage levels.
Comparing the grid with the Internet creates the impression that it’s a simple matter to add renewables to the grid, but the reality is far different, and the analogy is misleading.
Notes:
- For those who are not familiar with digital communications, a bit is an on-off signal, usually represented by a voltage, which requires the use of binary mathematics. A byte is eight bits.
- Collectively, the huge numbers of individual components use a great deal of power: 40 GW according to a calculation by Russell Seitz in 2006.
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