Solar and Wind - The Challenges
Recently a reader, Nadine, posted a comment with a question which sparked my interest. Instead of a long and badly worded comment, I thought I would elevate the answer to her question to a fully fledged blog post. I think that the question is a valid one which is worthy of investigation here and is a question that I actually wanted answers to myself.
Nadine’s question was "could someone explain to me why it is difficult to adapt solar/wind technology to the existing grid?"
So I will attempt to explain in a very general way what the issues are regarding these two technologies and how they can fit into a total energy solution. Now there is a lot of (mis)information readily found on the Internet regarding wind and solar, so we will try and stay away from those sources and concentrate on the simplest explanations wherever possible - there are probably hundreds of other points good and bad that can be made and I am sure our educated readers will happily pass on their knowledge in the comments section below.
The power industry faces a couple of problems from the variable natural inputs concept. The first is that of peak loads, and the second is that of reliable continual power generation. Solar obviously works best in clear skies and direct sunlight with clouds and other weather severely impacting generation, wind has the same problem. No wind, or low wind, equals no/low power generation. Depending on the type of technology it produces low voltage DC power that must be converted to AC at a very high voltage to feed the grid. However, some solutions such as Concentrated Solar Power (CSP) use a normal generator and can plug right into the grid, one example being the Solar One installation in Nevada.
Peak Loads, Increasing Demand and Constant Supply
The power grid itself is part of the problem in deploying renewable generation from solar and wind - it hates fluctuation in power inputs. The system is not nimble enough to react to demands and inputs fast enough to deal with the sudden drops that pure wind and photovoltaic solar experience due to changes in weather. Anyone who has experienced electrical grid power fluctuations during peak load periods can attest to how incredibly damaging it can be to electronics and electrical systems as they are exposed to inconsistent power levels which cause oscillations that can result in widespread grid failures.
The introduction of PHEV (Plug-in Hybrid Electric Vehicles) will further increase overall demand for electrical energy, as will changes in manufacturing as companies update to newer more automated and complex green technologies in an effort to reduce emissions. This rush to reduce emissions by the consumer and industry will create demand that will far outpace production and create longer peak periods that will put additional stress on the grid system.
The magic of electricity is in the constant supply of power to the end user. This is achieved through a load balancing system, we know as the grid, that diverts electricity to areas of demand. The limitation is that all grid management systems use a constant input model to correctly anticipate and divert electricity. Currently, renewable production cannot provide this constant supply without some form of assistance, such as the CSP generators that are coupled with gas heaters to supplement power generation in poor weather. Alternatively, wind installations will commit to far lower power input levels equal to the sustainable minimum generation over a period of time. You may have a 30Mw wind farm, but you would commit to 20Mw of sustainable delivery to allow for fluctuations in generation.
There is plenty of information available at the US Department of Energy on the challenges faced and the solutions required.
Looking to the Future
There is a kind of holy grail in renewables from variable generation sources, that is the ability to capture and store the generated excess power during high production periods. The problem here is that the only way to store this energy is in another form. Batteries can assist in load balancing, but currently do not have the capacity for sustained output, so the energy must be converted to another form for storage and use later.
Some proposed solutions include storage of excess electricity as heat energy, others suggest using the power to pump water up to a storage area for use in hydro generators. The ultimate problem is in generating enough excess to produce enough stored energy to satisfactorily compensate during low production periods. These problems can be solved - but we are not there yet.
In the end we currently cannot rely on wind or solar power to provide the base load power for the grid. Wind and solar is great for use in variable supplemental power generation that can be brought on-line to help with peak load periods or power low load times (which will be coming less as demand grows).
These two technologies are not new and have been proven to not be commercially viable as a primary energy source during the past 30 years of development. I know that everyone has read the green stories about people using solar and wind to power their homes without problems, what you do not read is that most of these people are connected to the grid as well to provide the additional power they require - without a stable and reliable fall-back power source they would not find it so easy to rely on their micro generation systems.
A final issue that I would like to address is that one of applicable feasibility. Not every region in the world can support these technologies, it requires a wind corridor and /or a favourable sunny climate to generate power from these sources. This severely limits where these solutions can be deployed and be successful, so as a primary solution they are not universal in their application.
There are many other technologies that need to be explored and enhanced to create a feasible pool of technologies that can be used in a variety of situations, but just calling for solar and wind is not going to solve the world’s energy problems on a global scale.
You know I agree with you on the whole, I would like to add a few bits though.
The feasible pool of technologies includes solar thermal and ground source heat pumps. The former of course has similar problems to PV, while the latter actually requires some electrical input. But despite the relative lack of sun in the UK, these technologies are being successfully deployed. Biomass boilers, and biomass fired micro-CHP, while problematic in the UK right now - much of which relates to lack of standards for pellet production and sale - also show some potential. Micro-scale water generation is an option for some.
These technologies can be invaluable to the fuel poor, providing independent decentralised and almost cost-free energy.
See e.g. csep.co.uk. One of the fun things they have been doing is taking used chip-fat from local fish’n'chip shops and using it for a fleet of diesel taxis. Another innovative project in the pipeline is using heat from local mines. There are probably a million innovative and feasible small-scale ways to re-use, reduce and recycle. Combined with efficiencies (insulation, passive etc) and behavioural change, and localised (city-wide where necessary) district heating and cooling from gas-fired CHP these measures can reduce CO2 emissions to well within the 60% requirement with relatively little fuss and bother.
The gas-fired district heating could of course be retrofitted with waste incinerators and even nuclear reactors, although I am still not convinced that nuclear is a necessary long-term solution to domestic energy demand (despite my upcoming blog).