This is to follow on from my post last week–I want to discuss Clark Miller’s ideas on how we will design the solar energy future, based on the article and video of his Dream Course lecture that were posted Friday.

The presumption of course is that solar energy captured by photovoltaic cells [note] is the energy source of the future. I will neither agree nor disagree with this presumption; for the purpose of this post I will assume that presumption is correct. My only comment is that, by not discussing this issue explicitly, I believe Dr. Miller concedes that any power source must be available at all times, i.e. the argument was not made that the environmental benefit of using solar was enough to justify intermittent power availability. Current storage technologies cannot support the large amount of energy that would need to be stored. So, unless the storage problem is solved, an intermittent power source such as solar must be supplemented with another non-intermittent source (or solar supplements another non-intermittent source).

In my last post I wrote that the following statement was controversial: “At least for the purposes of this transition, energy policy must expand to acknowledge, recognize, assess, and incorporate the fact that its objectives and outcomes are not just to change either the fuels or technologies of energy but to transform socio-energy systems.” In fact, there was a caveat to my statement about controversy. The caveat is that this statement is controversial only if we continue to have the vast majority of our electrical power generation concentrated, i.e. if electric power for thousands (or more!) of square mile regions is generated at one geographic location. A distributed power source will definitely require transformation of socio-energy systems. In fact, solar is different from almost all other large-scale power sources because solar can be distributed. Does anyone reading this blog know where their power is being generated (okay, if you are reading this blog at the University of Oklahoma you should know since power is generated right on campus, in fact across the street from my office!). In fact, the only time in my life I have known where my power was coming from is when I was at a University. The statement in Dr. Miller’s post that “Solar energy is a profound design challenge unlike any that humanity has ever faced” is a direct result of the fact that solar energy can be distributed.

Given current solar cell efficiencies and line loss, if solar captures more than ~20% of the overall power market in the US, I believe a significant portion of that power generation must be distributed. So the “can be distributed” from the previous paragraph should be “must be distributed to a substantial extent if solar power is going to capture a significant fraction of our energy generation capability.”   

Since solar will be at least somewhat distributed there are three issues that are unique, and present the design challenge stated by Dr. Miller. The first is ownership. Does the individual consumer own the equipment and the electricity; does a company own the equipment and the electricity; or does some governmental organization own the equipment and the electricity? (Note that the latter two are the models currently in use for electricity generation in the US, except for solar). Even if privately owned, electricity generation is highly regulated with respect to price etc.; will that continue in a distributed model? Lines are still needed; who owns the lines? Dr. Miller points out that whatever way is chosen will have a large impact on how solar power is perceived and used. 

The second issue is, where to put the panels? Possibilities include large fields, on water, on posts in cities, on rooftops, etc. From an engineering perspective, the closer the panels are to where the electricity is used the better (line losses are about 5% on average in the US). But for a distributed source like solar there is also an aesthetic perspective. Aesthetics are significant as Dr. Miller describes. Much of the resistance to wind power is driven by aesthetics. Solar power offers a unique and frankly unprecedented opportunity to integrate power generation into structural design. Here is a website that has 10 buildings which are impressive looking because of the solar panels. From a University perspective, are architecture courses going to have a component that talks about integrating solar panels into design?     

There is also a third issue which is related to the nature of solar power. Miller made the point that electricity prices will be cheaper in the day and more expensive at night, where the reverse is true today. Miller’s suggestion is that 24/7 operations might change. Industrially, I believe that benefits of using equipment continuously and the fact that the price difference will be small are important enough factors that operations will actually not change. But those businesses that are 24/7, and whose the costs are people and not equipment driven (e.g. Walmart), are more likely to adjust operations.

I would like to end this with a personal story. My house was built according to plans we purchased in 2004. I examined every energy efficiency measure conceivable. At that time, there were only two measures that made economic sense: polyurethane insulation and tankless water heaters. Every so often I look at adding solar panels. Where I live the payoff period (i.e. the point where the savings is equal to the upfront cost) is ~15 years with rebates.  A heat pump, in 2004, had a payoff period of about 10 years. I chose neither of these, because a rule of thumb with any equipment that one owns is 10 years, i.e. expect equipment to need major repair/replacement in 10 years assuming no regular maintenance. Anything less than 5 is typically a no-brainer (unless you plan to move) and 7 is typically a go-no go type of decision (the time value of money is also a consideration!).  

[note] There are other ways to use solar power other than photovoltaic cells.   The sun heats as well, and using the sun to heat (usually involves mirrors or lenses) is being explored.  Most of what is stated here is true for this method of using solar power as well.

Brian Grady (ORCID 0000-0002-4975-8029) is Douglas and Hilda Bourne Chair in Chemical Engineering and Director of the School of Chemical, Biological and Materials Engineering at the University of Oklahoma.