Category Archives: Energy & Technology

Using electricity from regenerative braking

Most rail mass-transit systems use electricity for motive power. The electric motors that accelerate the train can also be reversed to slow the train and generate electricity, which is called regenerative braking. Unless this energy is used immediately (another train is leaving the station at the same time as one is arriving), it typically is shunted to a bank of resistors and wasted as excess heat. However, a couple transit systems are finding economical ways to use this energy.

Philadelphia’s Southeastern Pennsylvania Transportation Authority (SEPTA) installed a lithium-ion battery system to store the excess power. They are able to make the investment profitable by accessing the frequency-regulation market. Not to get too technical, but the market prices for electricity greatly depend on the desired use. Base-load electricity (from traditional power plants) is cheap, but cannot accommodate sudden changes in demand. Frequency-regulating power is used to respond to sudden spikes or dips in consumption. (If this power is not available, the system cannot maintain the desired 60 Hz current, hence the name, frequency regulation.) Utilities will pay a premium for this short-term power supply to keep the overall system running smoothly. SEPTA now earns up to $200,000 per year as a power provider and has reduced energy use by 20 percent. The Scientific American article also discusses other storage technologies in Los Angeles and Portland.

The Dutch train system, Nederlandse Spoorwegen (NS), faces a similar dilemma to find a profitable use for their excess energy. Netherlands heavily subsidizes their commuter electrical costs to make transit affordable. NS pays approximately 1.5¢ per kWhr instead of the market rate of about 20¢ per kWhr. While this is great for Johann and Jaantje Commuter, there is little incentive for NS to implement new programs or systems to reduce consumption. As an alternative, NS is looking  to convert 30 diesel buses operating out of the Apeldoorn station to electric. The engineers cited in the Climate Progress article estimate that this will save about €8 million (US$11 million) over the next 12 years. Unfortunately, the article did not contain any specifics on whether this is an actual project or merely an engineer’s dream.

Hopefully, projects like these demonstrate viable ways to creatively use readily available but wasted energy.

New Carbon Regs coming 2 Jun 2014

Quite a few sites I follow have noted that Obama will make a significant policy announcement on Monday. He is going to propose regulations for existing power plants. These plants are the source of 40% of US’ carbon dioxide emissions, so the regulations could have a dramatic impact on the country’s contribution to climate change. I imagine most major news outlets will provide coverage next week, but there is lots of information already available, if you are interested.

  • Scientific American, reprinting Climate Wire, provides a semi-brief primer on the policy (1,300 words).
  • Brad Plumer at the new has a slightly longer primer (2,000 words). Plus, Vox has their “cards” to provide additional background and further reading sources.
  • There probably are shorter summaries out there, but the regulations will be complicated, so it is hard to cover concisely.

Predictably, not many talking heads are waiting to actually see the proposal before pontificating. The Chamber of Commerce has already issued a report saying that it will be the end of the world. Fortunately, this report has quickly been countered by two of my favorite writers, Jonathan Chait and Paul Krugman:

  • Chait at the New Yorker points out some of the questionable assumptions in the report.
  • Krugman at the New York Times highlights how the big scary numbers the Chamber tosses about are not really scary at all.

Long story short, the Chamber’s numbers are probably over-estimating the real cost. Further, even using the worst numbers, the US economy can easily cope and adjust. I’ve said it before, but the technical hurdles are solvable. There will be costs, but those are manageable as well. It is the drive and desire to overcome the status quo bias that is the only real problem.

Edit: 17 Jun 14, corrected spelling of Brad Plumer’s name.

Can You Have Too Much Solar? – Redux

I realized after my earlier posts on the solar power situation in Hawaii (Part 1, Part 2) that I had not done enough background reading. I was not wrong, per se, but had missed on some of the relevant context.

First, from Channel 2 KHON, that the Public Utilities Commission (PUC) had rejected Hawaiian Electric Company’s (HECO’s) Integrated Resource Plan (IRP). An IRP is typically a utilities long-term plan as to how it will continue and improve service in the coming years and decades. The PUC rejected the IRP, which is quite uncommon, believing that HECO ” is not moving fast enough to lower utility rates and connect more photovoltaic systems into the grid.” So, while there certainly are technical difficulties in connecting more solar, HECO needs to take much more action on solving those problems.

Second, Utility Dive provides a much longer overview of what HECO needs to do to modernize their network. One thing they point out is that this isn’t the PUC acting like a bunch of tree-hugging hippies, but that “the best path to lower electricity costs includes an aggressive pursuit of new clean energy sources.” The utility could install large solar PV facilities at a total cost of about $0.16/KWhr as opposed to about $0.23/KWhr for current generated power. So, HECO could provide solar electricity for about a third less cost than their existing oil-fired plants. Saving the planet is just a bonus.

Quick note: those aren’t electrical prices you will see on your electric bill, but raw cost of generation. From the Energy Information Administration, the average retail price for all US residential users is about $0.12/KWhr, while the average retail price for a Hawaiian is over $0.38/KWhr.

Can You Have Too Much Solar? – Part 2

In Part 1, I highlighted one technical issue with the increasing solar generation in Hawaii. Here, I want to discuss a misperception on an institutional barrier to distributed generation. When people think of electricity, they immediately picture their monthly bill and assume the utility makes all their money on the markup or profit margin per kilowatt-hour (kWhr) used. Like any good urban legend, that has a grain of truth. Consumers certainly are charged more for using more, but there are other utility costs that may or may not be rolled into that consumption rate.

The misperception is that Hawaiian Electric (HECO) is against solar because when more solar power is generated they do not sell as much electricity. But, that assumes the utility only functions on the hierarchical system where HECO just takes their cut in the middle:

  • power plant –> transmission and distribution –> user

But, if HECO ran a fully functioning multi-directional grid, they could leverage temporal and spatial differences in generation and consumption. During the day, HECO would buy the excess power from the home solar panels and sell it to downtown office buildings or regional industrial users. At night, HECO would then buy or generate non-solar power for people to turn on the lights, cook dinner, and watch Game of Thrones. The raw material (electricity) costs balance out as they are buying from and selling to different parties in different places at different times. HECO would make their money charging people to be connected to this grid. There still will be consumption fees (use more, pay more), but HECO would now be incentivized to operate efficiently in moving power around, rather than just churning out more of it.

Much of this has already been going on for years and will continue for many more. Deregulation in the 1990s led to splitting utilities into generating companies and distributing companies. HECO has added a fixed rate charge to cover their capital costs so it is not buried in the variable kWhr rate. Other companies are experimenting with tiered pricing and time-of-day rates. Ernst & Young recently published a small pamphlet encouraging utilities to modernize beyond the old hierarchy.

Obviously, there’s much more to all this (and way above my head). A robust smart grid will not be cheap or quick to build. Renewable power is still a tiny fraction of all power production. Legal monopolies like utilities are forever in conflict with consumers and regulators. But, like I tell everyone when I discuss these topics – the technical problems are comparatively minor and totally solvable compared to these matters.

Can You Have Too Much Solar? – Part 1

Recently, I’ve seen several articles regarding problems with having too much distributed power generation (e.g., primarily home solar panels, but also small wind) on a utility grid. The best example is the Hawaiian Electric Company (HECO) restricting installation of new solar panels in residential areas. Most of the article headlines were dramatically portraying HECO as the evil utility needing strict oversight. (The bald-headed villain, sitting in a high-backed chair, stroking a white Persian cat, is merely implied.) Green Tech Media has a much more balanced overview of the situation including the technical challenges, which I’ll summarize here.

Hawaii Maximum Daily LoadHECO is limiting (or at least delaying) new solar installations in neighborhoods where the daytime power generation exceeds the consumption. (Dark blue areas in map.) I emphasize daytime generation and consumption because this is where the conflict arises. Total electricity use peaks during the middle of the day when all the stores, offices, and factories are up and running. Solar generation peaks at the same time in the bright, mid-day sun. But, electricity use in residential areas drops as all the busy little worker bees are at those stores, offices, and factories. So, just a few solar panels will meet the daytime needs of a given neighborhood. If a couple of your neighbors beat you to the punch, you’re out of luck and probably peeved.

So, back to the question, Can you have too much solar? Yes and no (my favorite answer). The traditional grid system is hierarchical and unidirectional – from big power plant to distribution system to end-user. It is not built to handle flows in many different directions at different times of the day. So in the short-term, yes, too much solar could lead to problems.

Conversely, Hawaii is uniquely positioned to operate a renewable-energy smart grid due to high electricity costs (from burning imported oil), readily available renewable resources (ample sunlight, steady trade winds, and even geothermal on the Big Island), and relatively small size. In the long run, therefore, Hawaii can accommodate much more distributed generation. Until, that is, they generate more than they can use. But, let’s cross that bridge when we get there.

In summary, I agree with HECO in regulating the amount and size of new solar power to protect the overall system (regardless of any white-cat ownership). That doesn’t mean that I think the status quo is acceptable, but it does take time (and money) to transition to a better arrangement. In Part 2, I will cover the institutional and financial issues to get from the short term to the long term.

US Energy Flow in 2013

If the last post was hopeful, this one is more depressing. Every year, Lawrence Livermore National Laboratory updates the Sankey diagram of energy flow in the US. The flow chart may be a little confusing at first, but it traces all sources of energy (left) to the users (middle and right). The width of each line is proportional to the energy flow. The reason the chart is such a downer is that the lines for renewables are so much smaller than the fossil fuel lines. The yellow line for solar is basically invisible at the reduced image size below. There is a long way to go.

US Energy Flow 2013

Just to end on a better note, the diagram also shows a huge opportunity – the gray bar on the right labeled, Rejected Energy. About 60% of all the source energy is lost during processing and use as waste heat. This can’t be completely eliminated (I won’t get into the thermodynamics of it), but there is plenty of room for greater efficiency and energy re-use that can shift the loss ratio.