The mathematics of planet earth is a joint initiative from a consortium of mathematical sciences organizations around the world (organized nominally by DIMACS) that has the goal of showcasing how mathematics can be useful in tackling our world’s problems. It started last year as a year-long focus, but has now expanded and will continue for the coming years as well. I’ve been to a few events organized under this program, but the reason for this post is to highlight the recent workshop on “Data-aware energy use” organized at UCSD a week or so ago.
Energy and the environment are probably the most critical and massive problems of our time. The transformation of our energy system into a more sustainable form will take decades, determination, and sacrifices. In the case of power networks, several powerful trends are driving major changes. In this post, we will look at two of them.
The first trend is the accelerating penetration of distributed energy resources (DER) around the world. These DER include photovoltaic (PV) panels, wind turbines, electric vehicles, storage devices, smart appliances, smart buildings, smart inverters, and other power electronics. Their growth is driven by policies and incentive programs. California, for instance, has ambitious policy goals such as:
- Renewable Portfolio Standard (2002): 33% of retail electricity will be procured from renewable sources by 2020.
- Global Warming Solutions Act (2006): Reduce greenhouse gas emission to 1990 level by 2020.
- California Solar Initiative (2007): Offers solar rebates for customers of three CA investor-owned utilities, from 2007 – 2016.
- ZNE homes (2007): All new residential construction will be zero net energy by 2020.
- Energy storage target (2010): The three investor-owned utilities will deploy 1.325 GW of non-hydro storage by 2020.
Leading the world, in terms of percentage share of non-hydro renewable generations (at approximately 20% now), is Germany. Its relentless push for renewables, in the face of technical and financial challenges, will no doubt help find a way forward and benefit us all. See a recent New York Times article, where a proud German reader commented, “And that’s what I love about my country, it is a pain, it causes frustration and malice, but nobody questions the vision.” The question is not whether we should move to a sustainable future, but how we overcome the many challenges on the way (e.g., see Adam’s earlier post about Germany’s challenges), and the earlier we start, the less painful the process will be.
The second trend is the growth of sensors, computing devices, and actuators that are connected to the Internet. Cisco claims that the number of Internet-connected “things” exceeded the number of people on earth in 2008, and, by 2020, the planet will be enveloped in 50 billion such “Internet-of-things.” Just as Internet has grown into a global platform for innovations for cyber systems in the last 20 years, Internet-of-things will become a global platform for innovations in cyber-physical systems. Much data will be generated at network edges. An important implication on computing is that, instead of bringing data across the network to applications in the cloud, we will need to bring applications to data. Distributed analytics and control will be the dominant paradigm in such an environment. This is nicely explained by Michael Enescu (a Caltech alum!) in a recent keynote.
The confluence of these two trends points to a future where there are billions of DER, as well as sensing, computing, communication, and storage devices throughout our electricity infrastructure, from generation to transmission and distribution to end use. Unlike most endpoints today which are merely passive loads, these DER are active endpoints that not only consume, but can also generate, sense, compute, communicate, and actuate. They will create both a severe risk and a tremendous opportunity: a large network of DER introducing rapid, large, frequent, and random fluctuations in power supply and demand, voltage and frequency, and our increased capability to coordinate and optimize their operation in real time.
The typical story surrounding data centers and energy is an extremely negative one: Data centers are energy hogs. This message is pervasive in the media, and it certainly rings true. However, we have come a long way in the last decade, and though we certainly still need to “get our house in order” by improving things further, the most advanced data centers are quite energy-efficient at this point. (Note that we’ve done a lot of work in this area at Caltech and, thanks to HP, we are certainly glad to see it moving into industry deployments.)
But, the view of data centers as energy hogs is too simplistic. Yes, they use a lot of energy, but energy usage is not a bad thing in and of itself. In the case of data centers, energy usage typically leads to energy savings. In particular, moving things to the cloud is most often a big win in terms of energy usage…
More importantly, though, the goal of this post is to highlight that, in fact, data centers can be a huge benefit in terms of integrating renewable energy into the grid, and thus play a crucial role in improving the sustainability of our energy landscape.
In particular, in my mind, a powerful alternative view is that data centers are batteries. That is, a key consequence of energy efficiency improvements in data centers is that their electricity demands are very flexible. They can shed 10%, 20%, even 30% of their electricity usage in as little as 10 minutes by doing things such as precooling, adjusting the temperature, demand shifting, quality degradation, geographical load balancing, etc. These techniques have all been tested at this point in industry data centers, and can be done with almost no performance impact for interactive workloads!
James Hamilton has had two interesting recent posts about local renewable generation for data centers that are definitely worth a read for folks interested in “sustainable data centers”: Solar at Scale and Datacenter Renewable Power Done Right.
Sustainable data centers
It’s always interesting to hear perspectives on “sustainable data centers” from industry, because there is a big diversity still in how companies are moving to make their data centers sustainable. Some companies are going with a “local” approach, where renewable generation (in a variety of forms) is integrated on-site, while others are going with a more global approach, where renewables are placed somewhere else on the grid (often nearby, but not always). An example of the former is Apple and an example of the latter is Google.