New types of small gas turbine engines of under 100-Kw output that can operate on a wide variety of fuels have appeared. Some of these new turbine engines use turbine blades made from high-temperature ceramics such as silicon-nitride and silicon carbide that allow these engines to operate at higher combustion temperatures and at higher thermal efficiency. On-site power generation is appearing in privately owned off-grid homes as well as at commercial and industrial locations. As far back as the mid-1990's, a few commercial power users have installed natural gas powered truck engines (up to 300-Kw) on their premises to generate power and supply heat during winter (co-generation).
During summer, some owners used the exhaust heat from these engines to activate modern absorption air conditioning equipment. At other installations, the hot exhaust from micro-turbine engines was used to produce saturated steam at locations where steam was needed. This steam can also be superheated and expanded in small steam engines that drive electrical generation equipment. Heat in the exhaust steam may be used to heat buildings during cool weather. The overall energy efficiency of modern small-scale power systems could exceed 50%. Modern computer technology allows these systems to be automated whereas telecommunications technology can allow groups of such small (DG) co-generative power stations to be monitored and controlled from a single remote location.
Automated and remotely monitored power generation systems would incur low personnel costs and low overall operating costs. Mobile maintenance staff could be routinely assigned to inspect various power generation locations and perform minor maintenance tasks as needed. Such installations could serve groups of commercial users who are located within the same property boundary. Private power lines may be connected across private property lines with the owner’s permission and where regulations permit. Most small-scale power generation systems could be built so as to be easily removable and mobile, features inherent in low-power technologies such as fuel cell systems, solar photovoltaic systems and thermo-acoustic engines.
Larger, self-contained, small-site power generation systems could be built as shipping container sized modules that are either 20-ft or 40-ft long by 8-ft wide. This size would enable them to be easily transported on existing highway truck, railway and marine transport systems. A 20-ft module may contain a microturbine with its exhaust connected to a coil monotube boiler, a superheater, a small steam engine and a parallel flow steam-to-air condensing system. The largest modular mobile power generation systems carried by trucks would have a gas or air turbine housed in one module, a boiler (and superheater) in a second module, a steam driven power system in a third module and several modules containing condensing equipment. Alternatively, condensing equipment and steam-vacuum refrigeration (air conditioning) equipment may be built as permanent on-site systems.
The modular power generation systems could be designed to allow for quick and easy on-site assembly, easy disassembly and easy transport. Most large high-rise office buildings, major hotels and commercial centres are built so that trucks can be driven directly into their basements. Small-scale power generation systems built as container sized modules may be assembled and housed in these basement areas. Major overhaul or extensive maintenance of the gas turbine and the steam bottom-cycle engines would be done off-site. An auxiliary mobile generation system may temporarily supply power during an off-peak period while the gas turbine and steam power modules are disconnected are replaced with refurbished units. The ease and speed of the replacement process would greatly enhance the attractiveness and market acceptance of on-site, small-scale, modular (DG) power generation systems.
At locations where railway sidings exist, mobile power generation systems may be built on to rail vehicles. One rail car may house a gas turbine (air turbine for external combustion operation) and its exhaust may flow through a flexible/extendible duct into an adjoining rail car housing a boiler and superheater. A rotary steam engine driving electrical generation equipment may be housed in the same rail car or in an adjoining car. Steam condensing equipment may be built into several other adjoining railway cars. Alternatively, steam may be condensed using stationary equipment that uses exhaust steam to drive a steam vacuum refrigeration system. If solid fuel like biomass or coal is used (gasifier combustion), fuel may be delivered via hopper cars parked on an adjacent siding. Combustion ash would continually be removed from the fuel gasifier systems while power is being generated.
Rail-mobile power generation systems may be automated and be monitored and controlled from remote locations. Maintenance personnel would routinely inspect the power generation technology and undertake minor maintenance. Major overhauls, maintenance and repairs would be undertaken at specialised facilities after exchange rail-mobile power systems have been connected and activated. System exchanges would occur during off-peak hours. Power may temporarily be provided neighboring system or by appropriately equipped rail power units. While it would be possible for rail-mobile power generation systems to be built as self-propelled units, they may also be towed to and from specialized maintenance facilities.
There are locations around the world that are more easily accessible by river (or sea) than by road or rail. Power generation equipment may easily be installed into a variety of sizes of boats, barges and ships that can be tied to a dock for extended periods of time. Navigable rivers exist in many nations where marine-based power generation equipment could serve different local markets on a year round or on a seasonal basis. Fuel may be sent by marine transport to the various power generation sites. Advances in pebble-bed modular reactor (PBMR) nuclear technology can enable electric power to be generated aboard ships and even on rail-bound power generation systems.
If the long term leasing, fuel and overall operating costs of mobile power generation systems become sufficiently competitive over the long term, a market niche could develop for this technology. DG operations could subsequently become widespread in many nations due to fuel costs being the dominant cost of most thermal power stations. In most locations where private producers would serve commercial and industrial customers, private regulation may prevail and involve commercial attorneys representing the interest of providers and customers. They would negotiate binding agreements between the various parties and represent their clients' interests when disputes between various parties are resolved before judges in civil courts.
The development, evolution and operation of small-scale, on-site, distributed generation (DG) power systems in the commercial and industrial markets could bring new power online and ease projected future power shortages. Unexpected power shortages in populated regions would be eased if mobile power generation systems and their fuel supplies were quick to arrive and were quickly activated. Ice storms are notorious for damaging long-distance power transmission lines and interrupting access to electric power for large populations. The presence of stationary and mobile DG systems at such locations can become essential.
Power regulators in many jurisdictions forbid private power lines from being connected across property lines. This prohibition has discouraged investment in DG systems that could have been shared by several commercial customers located on adjacent neighboring properties. Regulation compels commercial power users to source their energy from distant power generation facilities that operate at lower efficiency than what can be achieved locally using small-scale, combined-cycle, co-generative systems. Regulators actually enforce inefficiency in power generation and they create hardship for communities that may be marooned after the long-distance power transmission lines are taken down by weather storms. Changes in regulation could go far in the future by allowing the unrestricted use of DG power technology.