I just finished attending the ENERGY 2013 conference in Lisbon. The conference was a part of InfoSys 2013, which consists of several smaller conference all bundled together. Each day had one keynote and on panel discussion drawn from all the different conferences/tracks, making for an interesting, and eclectic experience. There were perhaps 30 attendees for the ENERGY subconference, so I got to know several of the presenters.
I was presenting our paper on lessons learned from designing energy feedback visualizations for the Kukui Cup. Our three lessons about feedback visualizations is that they should be actionable, that domain knowledge must go hand in hand with energy feedback systems, and that this feedback must be “sticky” to lead to changes in behaviors and attitudes. While I was probably the only attendee focused on feedback visualizations and behavior, I got some interesting feedback from other energy attendees, such as finding additional ways to connect to undergraduates (e.g., beer :))
Below are my notes on some of the presentations I found noteworthy. So nice to be at a conference with open access to the proceedings so I can link to them directly!
Energy Aware Scheduling
Kanad Ghose presented on Dynamic Classification of Repetitive Jobs In Linux For Energy-Aware Scheduling: A Feasibility Study. 2.8% of electricity in the US is used by datacenters, and their research is on trying to find ways to reduce energy use in the datacenter environment. The basic idea is that some jobs are CPU-bound and others are I/O bound, so on a server with multiple CPUs, some CPUs can downshifted in voltage and frequency for I/O bound tasks (which spend most of their time waiting for I/O requests) with a consequent savings in energy. The other CPUs are kept at the highest performance level for the CPU-bound jobs. Each type of job (identified by the executable image) is classified, and jobs are scheduled by the kernel on the properly tuned CPU. Interesting work, and they are seeing about 5-10% reductions in energy use with small increases in latency. In the future they foresee servers in the data center communicating data about their loads (and predicted loads) to the HVAC system to further reduce energy use by preventing overcooling.
Voltage Sensors for Smart Grids
Chris Yakymyshyn from FieldMetrics presented on his work on Sensors for Smart Grids, which focused on the complexities of designing voltage and current sensors for the medium-voltage environment that are highly accurate. Utilities are typically required to provide electrical power within certain bounds of voltage and frequency. In the past, utilities had usually just targeted the center of the range for safety, but they have now realized that by reducing the provided voltage to the bottom of the regulated range they can save huge amounts of energy, avoiding the need to construct additional power plants! However, to skirt the edge of the regulated range, utilities need to actually measure the voltage they are providing so they can avoid fines for being outside the range.
One neat thing is that the sensors they have designed work optically, taking advantage of the Pockels effect whereby an electric field changes the index of refraction of certain crystals. Their sensor produces polarized light, which is guided through multiple crystals, and a sensor at the other end measures the angle by which the polarization light has been rotated.
The results from their field trials with BC Hydro are equally interesting. One major application by BC Hydro is detecting energy theft. To detect theft, a power sensor is installed on the medium-voltage transmission line before a group of customers, and then after the group. Combined with smart meter data from the customers, the utility can determine how much power should have been drawn off the medium-voltage line compared to what the smart meters reported. In one neighborhood, approximately 27% of the delivered electricity was being stolen, and the majority of that was coming from (illegal) marijuana grow operations! This leads me to ponder how much energy we could save if growing marijuana was legal, which would allow for more outdoor growing, or at least energy audits of facilities.
Energy Storage & Vehicle-to-Grid (V2G)
Mark Apperley from the University of Waikato, New Zealand brought a wonderful discussion on energy storage and specifically vehicle-to-grid (V2G) storage. One of the conference panel discussions focused on energy storage. The discussion was quite wide-ranging, and I found the following points interesting
- Mark pointed out that we all have a storage system in our homes for a different resource: toilets. Toilets store water, dispensing it at 140 l/m, but refill at 30 l/m. The water storage provides two benefits to water-providing utility: it smooths out the load generated when people flush, and it also provides an “infrastructure improvement” since the water pipe coming to homes is not sized to provide water at the rate needed to flush. Electricity storage would also provide these same two qualities. For example, as electric vehicles become more widely used, the distribution lines to neighborhoods may become overburdened as adding an electric vehicle roughly doubles the electricity use of a home. In a neighborhood with many EVs, some vehicles may discharge to provide their neighbors with power which the utility is not able to provide with the existing distribution lines.
- In talking about the growth of renewable energy, Chris Yakymyshyn pointed out that fossil fuel power plants need to run a certain percentage of the time in order to make a profit. If they are only being used a small percentage of the time to support intermittent renewable energy sources, they will shut down and go bankrupt.
- I shared point made by Mark Duda, a founder of residential-solar installing company RevoluSun in Hawaii. He pointed out that since electricity prices are very high in Hawaii, PV is quite cost-effective for many homeowners, some of whom also install a battery storage system so they can go completely off the grid. Hawaiian Electric (like all utilities) has large fixed costs (power plants are expensive!) that it has to pay regardless of how much electricity they actually generate. Thus as more people are able to switch to solar, Hawaiian Electric will have to spread the fixed costs over fewer customers, leading to higher rates. This makes solar cost effective for even more homeowners, who then disconnect from the grid, which could lead to a spiral when the utility can no longer afford to pay its fixed costs.
Mark also gave a keynote talk on his research into V2G in New Zealand. The concept of using electric vehicles as a storage system for the grid is not new, as it was first suggested by Kempton and Letendre in 1997. Two important issues for V2G are that the electric vehicles need to be plugged in to be a resource for the grid, and that the decision on whether to charge from the grid or discharge to the grid requires knowledge of the planned usage of the vehicle (e.g., when will the owner be driving home?).
The promise of V2G is that vehicles are only used a small portion of the time. In NZ, vehicles are estimated to be used only 4% of the time, providing a lot of potential time for grid backup. Mark has created a fine-grained simulation of electric vehicle use for grid storage in NZ, with a 1 minute time scale, individual vehicle simulation, and real utility load data (we can only dream of this level of data in Hawaii!). The simulation also takes into account the gradual adoption of electric vehicles.
Based on the simulation results, with 400,000 EVs, V2G reduced peak energy generation requirements, and flattens out the demand curve. Unfortunately, it did not actually reduce the height of the peak load: while EVs can be helpful for storage, they also increase demand for electricity for their use as transportation. As an amusing aside, Mark said that one of his student’s had computed that if all the laptops in NZ could be linked to the grid, they would be able to handle the national load for a few minutes
It would be great to see a simulation of how V2G would work (or not) for Hawaii, but it would require a lot of data that is not available outside of Hawaiian Electric.
Mahalo to all the participants and organizers of ENERGY 2013!