Electrical Grid of the Future
The following is an update I posted on LinkedIn in February 2015
Infrastructure, Options, and Centralization
"Infrastructure" is a word we often hear from politicians when they want to spend billions upon billions to engage in "economic stimulus" and transportation projects which often result in little long-term change for the better. Other areas of infrastructure such as telecommunications, sewage treatment, and waste disposal are usually so well managed that we forget all the work and technology which goes into keeping them running problem free every day. The electrical grid holds a unique position, being the most important yet the least important infrastructure area we have; almost all of the others can't function without electricity, yet it is more a luxury than necessity for human survival.
I will start by stuffing my thumbs in the eyes of both those who scoff at passive production (referred to by the misnomer of "renewables") technologies, and those who assume the only future is one without "Big Oil" and "fossil" fuels. If we are to move forward, all technologies must be harnessed where their strengths and/or conveniences make them the most suitable option. For example, a wind installation is not the best-suited method for powering an aluminum smelter. A coal plant is not the wisest option to place in urban or suburban areas.
Our current system is one of centralization and economies of scale. Power plants with capacities in the megawatts and gigawatts churn out electric current, sending it over high voltage lines and stepping it down to lower voltages before distribution to the consumer. This method has been developed and tested over a century and has no major faults, that is, until the weaknesses of the system are considered.
From the perspective of reliability and emergency management, the strength of our electrical grid is also its weakness - centralization. In times of catastrophe decentralization is key; however, decentralization is also the way of the future. Power must be produced as close as possible to the point where it is consumed; preferably at the point of consumption. This can be as simple as employing battery-backed photovoltaic (PV) to provide electricity for lighting and non-critical systems, something which accounts for over 10% of electricity consumption in the US. Decentralization is key, but how do we implement it?
Consumers Are Not Created Equal
We must consider three categories of consumer: industrial, commercial and residential. Industrial consumers are those who require large amounts of power and whose demand usually remains at a constant level. Commercial consumers typically require medium amounts of power but have cyclical demand. Finally, the demands of residential consumers are cyclical and low power. We focus on residential consumers, as this is the area where the most changes will occur, and many of these changes also apply to the other consumer types.
Battery-backed PV, along with small generators or wind turbines, will fulfill the power needs of most residential consumers. The day when your "utility closet" becomes a true utility closet doesn't seem that far off for those who are forward thinking. Implementations will vary depending on power requirements and individual tastes, but tomorrow's utility closet will house a battery bank, power inverters, grid-tie equipment, a home's control system, and possibly a small hydrocarbon-powered generator. A home's roof will turn from passive structure into the home's primary power generator through the use of PV systems. Some homeowners will also install small wind turbines in the 1-5kW range to supplement solar during inclement weather, while others opt for a generator, or turbine and generator.
Industrial consumers will continue to rely on traditional central production for primary power, often from hydrocarbon, hydroelectric, or nuclear sources. Technologies such as blast furnace gas generators will turn consumers into net power producers. Secondary power will come from roof-mounted battery/PV systems.
Commercial consumers will straddle both ends of the generation spectrum. Larger consumers and those who require 100% uptime, such as banks, will remain connected to traditional centralized sources. The remainder will take an approach similar to that of residential consumers.
It Starts Outside the Wall Socket
There is a price to pay when converting electricity from AC to DC and vice-versa. In battery and PV systems the penalty is often twofold: the conversion of DC battery or PV current to AC line current, then back to DC within devices such as computers. The solution is to manufacture appliances which require only DC, and to implement and standardize DC line voltages for use by those appliances. Voltage levels of 12, 24, and 48 volts DC are a good start; however, the beauty of the system is that voltages and currents can be configured on-the-fly to suit the needs of a particular device.
A home's power system must be capable of reliably forecasting the maximum power requirements for both peak (current draw when loads such as air conditioners are switched on) and average demand. All of this must be accomplished while retaining the current electrical sockets and AC line voltage capabilities.
How does all of this happen? Many appliances in the home already contain microcontrollers, and it is a trivial matter to incorporate the required power electronics and power-line communication (PLC) capabilities into new devices. The process begins with the outlet and line itself, where several options are available according to cost and complexity. The simplest, from a wiring perspective, is similar to current systems where all outlets on a circuit breaker share common wiring. The next implementation has each plug on an outlet sharing common wiring, while the final solution provides dedicated wiring for each plug.
Moving away from the outlet and into the utility closet, we find one or more power inverters. The most simple system has one inverter for each set of line wiring in the home, while the most complex contains an inverter for each plug. In addition to providing a default 120VAC, the inverters are also capable of supplying the required DC line voltages.
Traditional "dumb appliances" don't communicate with the home's power system at all, expecting a line voltage of 120VAC to be available. Smart appliances will communicate their optimal voltage and current parameters to the home's power system so it can tailor individual plugs, outlets, or lines to fit the profile as well as operate more efficiently. How this works is out of the scope of this post.
By making electrical devices and buildings utilize energy more efficiently, we can reduce the amount of demand on the electrical grid and decommission unneeded power production facilities.
A Network of Grids or a Grid of Networks?
Nothing covered thus far is new, many homes and businesses have made the partial or full switch to PV, but the real changes lie in the grid itself and the way electrical devices interact with it. The role of today's power companies will shift slightly away from power generation, towards network management, maintenance, bidirectional metering, and billing.
At the local level, the grid will resemble a computer network, each consumer tied in to the "local area grid" (LAG) much like a microgrid. In this arrangement consumers within the LAG are effectively isolated from those outside the LAG. Power transfers between members of the LAG occur automatically. Each member sends real-time power availability statistics to the LAG controller. If one or more member's statistics go negative, the LAG will gate power from members with excess capacity to compensate. For example, at some point in time a home may require more power than its systems are capable of delivering. A home's control system and grid-tie equipment will sense this condition and send a power request to the LAG, which will in-turn request power from homes which have advertised excess capacity.
LAGs are connected to each other, and to larger individual consumers, through primary area grids. PAGs see LAGs connected to them as individual members rather than a grouping of consumers, and like LAGs, allow transfer of power between PAG members. Higher levels of distribution networks include subtransmission area and transmission area grids, each functioning in a similar manner to a LAG.
A possibility which opens with LAGs is the ability of LAG members to own the LAG to which they belong. For example, a LAG is built within a new residential development. In this development a portion of the homeowners' association (HOA) fees go towards contracting LAG operation and maintenance to a third party, while the LAG is owned by the HOA. Those who own LAGs can set the conditions under which power is permitted to enter and exit their networks, taking into account things like times and prices.
Each member of a LAG will have the option to set the price they are willing to pay for power they request from the LAG, as well as the price of power the supply to the LAG. Solar may be sold at a lower price, while power generated from hydrocarbons may fetch a higher price. Pricing also affects the import and export of power to and from LAGs. For example, a member requests power and is willing to pay $0.12 / kWh for. The lowest price within the member's LAG is $0.14 / kWh; however, the LAG knows it can import power from the PAG for $0.12 / kWh (including tolls and other fees). A request is issued to the LAG with excess capacity, which in-turn requests power from the member selling it for the target price. The requested power is placed on the source LAG, travels through the PAG, and into the consumer LAG.
Building the electrical grid of the future is more than just shifting to newer technologies and updating transmission systems, it is changing our consumption habits and rethinking how buildings interact with various forms of energy. We must act responsibly and care for our surroundings while understanding that hydrocarbons are the most energy dense and portable method of energy storage. True energy independence is the refusal to rely on distant power production you have little or no control over, regardless of how said power is produced.