Why look beyond the grid?
Most industrial sites buy electricity from a utility. Some generate part or all of their power themselves. Common reasons include a remote location with no connection, a need for backup during outages, a wish to reduce cost or emissions, or a process that produces useful heat. None of these reasons guarantees savings, since results depend heavily on local prices, rules, fuel supply and the site’s load pattern. This article compares the main alternatives in general terms.
On-site engines and generators
Reciprocating engines, usually diesel or gas fueled, turn generators. They are well understood, start quickly and are available in many sizes. They suit several roles.
- Standby. Backup for essential loads during a grid outage, as in standby generators.
- Prime or continuous. The main power source for sites without grid supply, discussed under prime power generators.
- Peak support. Running at times of high demand charges where rules and economics allow it.
The costs include fuel, storage and delivery, maintenance, emissions controls and noise. Regular upkeep matters because engines used mainly for backup still need testing and servicing; see generator maintenance.
Gas turbines
Larger sites may use gas turbines, which suit steady, high-output duty and work well with heat recovery. They have higher complexity and need specialist support, as described in the overview of gas turbines.
Cogeneration (combined heat and power)
A cogeneration system generates electricity and uses the engine or turbine’s waste heat for steam, hot water, space heating or process needs. It makes sense where a site has a steady demand for both. Where heat demand is erratic, much of the benefit can be lost. The heat-use side links to waste heat recovery, and the arrangement requires careful engineering of both the electrical connection and the thermal system.
Solar
Photovoltaic panels convert sunlight directly to electricity. On industrial sites they are often placed on roofs, over car parks or on adjacent land. Features include:
- No fuel, little moving equipment and modest upkeep.
- Output that follows the sun, so it varies by hour, season and weather.
- A natural match for daytime loads, such as cooling or daytime shifts.
- A need for inverters, protection and a safe grid connection. Rules for connecting generation to the utility usually require approval.
More detail on the topic is in the benefits of industrial solar power. Solar alone cannot supply a site at night unless combined with storage or another source.
Wind
Wind turbines work where there is a good wind resource and enough space and permission. Output varies with wind speed, and siting studies take time; see the general explanation of wind turbines. Small industrial turbines and utility-scale ones involve quite different projects.
Storage and hybrids
Batteries and other storage can smooth variable output, cover short outages and shift energy between times of day. Many practical systems are hybrids: for example solar with batteries and an engine, or the grid with an engine for backup. Control systems decide which source supplies the load at each moment. Critical control equipment might also need uninterruptible power during switchovers.
How to compare options
A fair comparison asks the same questions of each option.
- Load profile. How much power is used, when, and how much is critical? A load study is the base of every decision.
- Reliability needs. What does an hour of outage cost? That helps determine the redundancy.
- Fuel or resource. Is fuel supply secure? Is the sun or wind adequate?
- Capital and operating costs. Include maintenance, fuel, replacement and the cost of money, with realistic assumptions.
- Space, noise and emissions. Local permitting often decides what is feasible.
- Grid rules. Connecting to the utility, or exporting power, has technical and contractual requirements.
- Skills. Who will operate and maintain it? Some options need specialist contractors.
- Efficiency of use. Reducing demand through energy management systems may be cheaper than generating more.
Safety and expert input
Generation equipment stores energy as fuel, pressure, heat and electricity, and connecting it to a site’s wiring creates risks if done wrongly, such as back-feeding power to lines that others believe are dead. Installation, protection settings and utility connection must be handled by qualified engineers and electricians, following the manufacturer’s instructions and local regulations. This article is a general introduction only.