Energy Storage at the Home and Office

Energy Storage is always the shoal upon which new energy use pattern run aground. Energy storage is what can disconnect us from the increasingly fragile grid. Energy storage would let the nation’s transmission lines work around the clock, increasing their capacity server fold.

Energy storage is what will make local generation deliver honest pay-back. Energy storage is what will align sunny day-time generation with home occupancy at night. Energy storage will let the home and factory trade freely in power markets.

Energy storage is so important, we have given it a pet name. We call it “The Hydrogen Economy”. But an actual hydrogen economy, like actual commercial fusion reactors is always, it seems, a decade or two away.

The shimmering vision of the hydrogen economy blinds us to how close the real solutions are. We have numerous ways to store energy today, from electrochemical to thermal mass, from raised ponds to bathtubs in the attic. We even have, well, old fashioned Hydrogen, good enough to work in the home, if not the car. Let’s call these amazing technologies batteries.

The battery economy won’t get its name on the cover of any magazines, but it’s the right place to watch. New kinds of batteries may come out of the places we are not looking. Peter Drucker once wrote that a new technology must provide a factor of 10 improvement in cost over the old to overcome the economic infrastructure supporting the old. Small improvements in existing batteries and simple rethinking of existing processes may always stay ahead of Hydrogen.

So where might we look?

Battery efficiency is properly understood not from anode to cathode, but from battery input through the device powered. Home and office DC power distribution can improve the practical efficiency of any battery by removing a round trip between DC (battery) to AC (to the plug) to DC (to supply today’s electronic devices). Improving the effective performance of a battery by 30-50% makes many technologies more viable.

Information technology is making long known methods to transform energy into suddenly new approaches. Stirling engines, for example, are a Victorian-era oddity that has amused generations of high school physics classes. Place one in your hand and the rotor spins – using the temperature difference between your hand and the room. Stirling engines are now coming into their own. Stirling Energy Systems has recently added a very large solar–based system to the western power grid. A commercially available home system recaptures waste heat from domestic hot water and space heating and generates electricity – and it can work on temperature differentials of as little as 15 degrees.

This makes thermal capture and storage an exciting part of the electrical mix. I can capture heat now to generate electricity now or later. I can store the electricity I generate for use now or later.

We may develop completely new approaches to thermal storage. One large solar facility in Spain uses mirrors to focus light and get temperatures high enough for generating electricity using traditional steam. This technology was made possible with embedded intelligence that allows a mirror array to constantly adjust to the current sunlight. Excess heat is stored by melting salt; the high heat molten salt is used to generate power later. Can this approach be scaled to the home or office? The most critical element is the software, which costs little to reproduce.

When we combine on site generation and distribution and use, it is called a microgrid. Microgrids become many times more reliable and economical with even a little on-site storage.

The home and office of the future will have its own microgrid with storage. A software agent will operate the microgrid while negotiating with the building systems to manage energy use. The agent will listen to the power grid to get up-to-the-second energy prices. The agent will be under the control of the building owners and occupants, responding to their wishes rather than to the wishes of the power company.

EnergyStar Systems and Data Centers

Data centers consume huge amounts of electricity, much of it wasted. Data centers convert electricity to heat, so all energy used for computing is paired with a similar load for heat removal. Rethinking data centers is a good way to make a strong impact on energy usage in a hurry.

All computers use direct current (DC) to actually run. So does most consumer electronics. That little brick, or wall wart on the power cord transforms power from the alternating current (AC) of the power grid to DC to be used by the computer. In most desktop computers and servers, that “brick” is internal to the computer. Improving this process is straight-forward, and does not require any fundamental re-engineering of the computers.

Recently I was reading that the EPA is proposing higher efficiency standards for power conversion efficiency in computer systems. Most systems today still have not met the current version of these standards, called EnergyStar. What caught my eye was how much power is wasted even in today’s EnergyStar compliant systems. The numbers are so large that they make the case for re-thinking power systems for data centers far stronger than I had thought.

EnergyStar standards require power supplies are that no more than 80% efficient or better. This means that to be compliant, no more than 20% of the A/C power coming to your data center computer be converted to heat and lost before it even gets to the computing circuitry. This lost power is converted to heat before it ever gets to support actual computing.

This increases the arguments for Direct Current (DC) data centers. DC Data Centers convert Alternating Current (AC) power to DC before it is distributed to the servers. Telecommunications has longed used DC distribution for its big racks. There are several processes that can be improved by re-thinking power distribution in data centers around the principle of DC distribution.

All of that power lost by conversion is today heat lost in the data center. That heat must then be removed to keep the computing equipment sufficiently cool. Air conditioning is one of the most significant costs of a operating a data center. Many estimate that it takes up to 1.7 times as much energy to remove heat from conditioned space as the initial energy that generated the heat.

By simple moving the AC/DC conversion outside of the conditioned space of the data center, 20%-40% of the heat is moved out of the data center where it will not need to be air conditioned away.

Many reputable companies sell data center batteries to support uninterrupted power. These usually have AC converted to DC to charge batteries, with the same losses as above. The servers run off batteries. The batteries supply DC, which is converted to AC (5-15% loss of power as heat) to support the AC servers. The power supplies in the servers then convert the AC to DC (as above, with loss of power and generation of heat).

When people discuss the efficiency of this process, they usually describe the efficiency of the battery storage as the limiting factor. What the process above shows, however, that as much as half of the power stored may be lost as heat though the double conversion before it ever gets used for computing.

In a DC data center, the batteries still supply DC power, but all of it goes directly to the servers. Not only does this generate less heat, but it can as much as double the effective efficiency and life of the batteries by removing the double conversion for the last yard of distribution.

This increase of efficiency comes with today’s technologies, without waiting on the perfection of any novel or exotic battery technology.

It is hard to use the waste heat from Air Conditioning. A large AC/DC transformer, however, concentrates the energy lost as heat into one place. It is easy to harvest heat from a single very hot location. I have even seen proposals for fueling a steam distillation chiller off waste heat from a transformer to provide supplemental air conditioning for a data center. You could run domestic hot water heating off the external transformer. I suppose you could even hook a Stirling engine to the transformer and light the building using the waste heat.

We do not have to wait for exotic technologies, although they will come. We need to re-think processes with an awareness of power at each step. Transactive pricing for energy will encourage us to do just that.

Grid Interop Coming up

I submitted an abstract for a talk at Grid Interop today. I have been near academia too long. Abstracts bring out the most pompous side of my writing. Even so, I am sharing this abstraction with you.

Business Innovation and Service Abstractions

True Scalability and interoperability require abstraction and security. Most control systems today expose name/value tag pairs as their interface. This poses two problems. Interaction with exposed tag pairs requires a deep understanding of the underlying systems. Secure interaction with sets of tag pairs can only practically be exposed as monolithic yes/no decisions for the entire set.

The smart grid will require integration with smart buildings and their associated power capabilities. We will need to develop abstract models for system interaction to enable such large-scale system integrations. These abstract models will hide underlying system detail while exposing the diversity of systems for orchestration.

None of this will happen without mature security models. Significant segments of people and businesses will not give up autonomy over their private resources to any third party. System abstractions will make building systems appear as printer drivers do, exposing themselves to owner agents able to negotiate with the intelligent grid.

A service can abstract the operations of each system. This service defines the mission of the internal operations each system. Each building system should defend its mission. Systems that are quite different in complexity and technology can provide the same service. Owners and integrators will be able to compare different systems as to how safe, effective, and economic their operation is without changing the higher level integration.

Services enable security, and security enables allowing the tenant or owner to interact with building systems. Agents can be restricted to which services they interact with, and what performance they request using understandable business rules. This level of abstraction will support internal tenants or third party service managers to safely and effectively interact with the building systems.

Service oriented architectures and integrations make possible large scale interactions. Service discovery enables ad hoc interactions. Services hide implementation details. Service oriented architecture to will enable orchestration of building systems including site-oriented energy generation and storage. New business models will take advantage of these new interactions to drive energy use reduction through innovation.

Treating Systems like Components

We tend to over integrate systems. In particular, we over-integrate building systems in high performance buildings. Because they all use similar signals, and have similar digital processing, the highest standard seems to be to integrate many systems as if they were a single system.

Each system should drive its own, and only its own, internal processes. Each system has a mission, a service it must perform for the enterprise that owns or inhabits the building. That mission drives the technologies chosen to compose the system.

The mission and the technologies drive the internal processes of each system. Because these processes are hard to do, and harder to do well, practitioners tend to think they are the most important part. Actually, no one cares, or should care, about the processes except from the inside.

Users and beneficiaries care only about the results of that process, what we call the service, and the requirements of that process, whether we call them inputs or call them costs.

The best way to integrate systems into a performant building is to ignore the processes, and to integrate the systems. The inputs must have clean interfaces so we can orchestrate the service provision. We must catalogue and understand the costs in resources and in waste. Thereafter, we should ignore the processes internal to each system during integration.

In business processes, bookkeeping is critical to any business. Accountants devise the processes for bookkeeping to make sure they accurately reflect the needs of the organization and that they produce accurate descriptions of business performance. Finance has to assume that the bookkeeping was done well, that the financial statements were well designed, and uses them to support higher level processes within the enterprise. Finance suffers if it focuses back on the Point of Sale.

Chris Martin, my friend who started his career in the Back Island microgrid, has recently examined the “energy financials” of systems in many research buildings. At UNC, we have central provision of steam and chilled water. Each building pulls its heating and cooling from the central distribution loops. It is an unfortunate truth that every building consumes heat in the form of steam, even in summer, and every building consumes cooling, in the form of chilled water, even in winter.

We have skilled staff who examine the energy-using systems in these buildings, and work hard to optimize them. This work is imbued with the deep processes of each system, and with the logic of the processes. Chris recently embarked on a different approach.

Chris began examining the “Energy Financials” of each building. As we work to break down silos between business processes, we are seeing for the first time, time sequenced data on energy use by each of the systems. In this analysis, the processes are hidden. All we have is the requirements and output from each system. The removes clutter and lets one see higher order interactions.

What Chris recognized is that the Chilled Water and the Steam consumption lay nicely on top of each other. For some months of the year, they could cancel each other out. During winter or summer, one fits entirely inside the other. This insight replaces fiendishly clever interactions with a simple one.

Chris is proposing a simple heat pump, or chiller, if you will, connecting the two systems. It will pump heat from whichever system is dominant for the season to the other one. It may enable some buildings to leave the steam distribution entirely. Payback on the small investment looks like it will range from 1.3 to 1.5 years, with a positive cash flow thereafter.

This is the advantage of hiding the processes, and looking only at the services and costs. The complexity of the problems you or someone else has already worked goes away. The opportunity for new solutions can be seen in the newer simplified set of facts. Chris Martin is demonstrating the advantage of approaching performance and efficiency of embedded building systems from the perspective of service oriented architecture.

Cool.