The transmission losses from power-plant to the load are a function of the number of transformers and miles of wire between them. In a minimum 2- transformer system short-haul it's on the order of a 3-5% loss, but on US type grids with averaged long-haul losses it'll be more like 7-8%. Wtih overloaded/underbuilt developing-world grids or the north American grids in full brown-out mode the transmission losses can exceed 20%(!).
With distributed mini & micro generation the transmission losses stay well bounded. But with intermittent sources like solar & wind that have only modest correlation with grid loads at best there needs to be some other more controlled sources to keep the grids stable. Denmark, the Netherlands, and Germany are achieving a remarkable fraction of renewable grid source power without resorting to centralized control, but to boost it well beyond 50% there needs to be a responsive grid-stabilizing power source. In Germany the utility Lichtblick is taking it that extra step with centrally controlled distributed home/building sized VW-powered gas-fired mini-cogenerators and thermal buffer tanks (to store the thermal output until there is a local thermal load in the building.) Their goal was to get a full nukes-worth of cogen on the grid in short years as a means of "hardening" their wind resources regionally. This works better in heating-dominated Germany, where grid load and heating system load rise and fall pretty much together than it might in other situations. Distributed gas-fired fuel cell banks such as Bloom Energy's offerings could do a similar hardening in cooling dominated climates.
Solar phovoltaic has a reasonable correlation of output to air-conditioning loads, but unlike with cogen/space-heating there's a phase shift of a few hours between peak output and peak load. Smart-grid control at the load could mostly realign that with pre-cooling based on real-time weather modeling, but SFAIK there hasn't been a big push to make every air-conditioner & chiller smart-grid enabled to pull that off. (Works great on paper though.)
Micro-wind on rooftop sucks by almost every measure (effiency, cost, output, reliability), but mid and large sized wind is quite reasonable where there's a resource. In the US the Great Plains wind is great, but it requires lossy (and non-existent) long-haul transmission to get it to the loads. Offshore (particularly on the eastern seaboard) the prospects of placing the wind farms nearer the load seems more plausible, but it's more expensive to develop land-based transmission lines than under-sea cabling. Roughly half the capital cost of large scale wind is in large scale transmission line development to bring that power to where it's used. Unlike solar, or cogeneration, wind has no reasonable correlation with specific load peaks, but over a wide enough region has a reasonably predictable & stable output. If/when it's necessary to ramp up a big fossil burner or nuke to carry the load IS possible to schedule in advance.
Cheaper (and quicker to develop) than any of it though is buying efficiency at the load end. Unlike massive rooftop solar, mitigating consumption with EFFICIENCY is often cost-negative, paying for itself in reduced utility costs over fairly short time frames, but energy use isn't near the top of most consumers' agenda when making capital investments. Getting grid operators to pay for the investment in the customer's equipment requires a fairly big shift in the regulatory environment, and an increased awareness on the customer end. A fairly decent academic/economic analysis of that problem can be found here: http://www.rmi.org/cms/Download.aspx?id=1366&file=E08-01_NuclearIllusion+(1).pdf&title=The+Nuclear+Illusion
Viewed from lifecycle costs, the net present value of efficiency investments blow any sort of generation source investment out of the water, but the time frames of the customers who use/own the equipment are much shorter than a typical utility's investment, and since energy costs are a small fraction of most business & family situations, it's a back-burner item. Incentivizing utilities with profit margins for money spent on rebates on higher-efficiency customer equipment has been (sorta) working in CA & MA and a few other states, but that's just the first thin-skin of the onion for what should be mid and long term financial sensible. It's also arguable that Germany's 30cents/kwh (wholesale) incentives for renewable power ISN'T financially sensible, but it gets the projects built (an fast!). The average RETAIL rate for power in the US is less than half what Germans pay their solar PV operators wholesale. This is not an easy nut to crack without raising the price of energy. |