Intro to Distributed Generation and ConnectTheGridTM
This month, Tesla started taking orders for their new Solar Roof product: individual solar panels as a replacement for your roof’s shingles. This product, along with traditional roof-mounted solar panels and other forms of small-scale power generation like wind turbine systems, are referred to as distributed generation – decentralized power generation that is collocated where power is used (e.g. at your home) instead of at large, centralized power plants. In working with our many electric utility clients, West Monroe observed a common problem: no software product existed to aid in the utility process of interconnecting these distributed generation assets to the electricity distribution grid. To address this problem, we built ConnectTheGridTM.
The enrollment module in ConnectTheGridTM solved the biggest problem our utility clients were facing: ingesting information about customers’ proposed distributed generation systems and automating the approval workflow electronically. Using our product, utility customers (or their solar developer) can self-register for an account, submit the necessary details about their proposed system, and receive notifications as the utility advances their proposal through the approval process. On the utility side, interconnection managers can easily perform their job duties around reviewing applications for completeness, routing applications to different departments, and ultimately approving customers to install on-site power generation equipment.
Part of that approval process involves utility engineers ensuring that the electric grid segment (called a feeder), which is affected by the customer’s proposed system, will continue to operate in a safe and reliable manner after the new system has been added. In short, assets like a customer’s Tesla Solar Roof directly affect the utility network; yet, these engineers are unable to determine exactly how much power these assets are generating as interconnected systems exist “behind the meter,” and thus, outside of the utility’s purview.
To inform engineers as they make these critical grid decisions about whether to approve or deny customer requests for installing on-site generation systems, we developed the Technical Screening module within ConnectTheGridTM. A cross-functional team of West Monroe technical architects and developers, project management and process experts, and electric utility subject matter experts came together to solve this problem for our utility clients. We discovered that there are two key inputs for utility engineers to approve distributed generation systems: 1) the proposed system’s estimated power output and 2) the ability of the grid to accept power generation from the proposed system without causing safety or reliability concerns (a concept called feeder hosting capacity).
Estimating a Proposed System’s Power Output
This estimation model is similar in concept to other tools like PVWatts, developed by the National Renewable Energy Laboratory to help consumers plan their distributed generation systems.
After our Technology team built the first iteration of the model and released it to our electric utility experts for testing, we found that our model broke down as the sun would approach the horizon. Specifically, this was due to an approximation we were using for calculating air mass – a component of the power output estimate that accounts for light scattering and absorption in the atmosphere. Our utility experts did some research and found that the Pickering model (Figure 1 below) for calculated air mass better approximated reality near the horizon. This is just one small example of how West Monroe teams blend functional knowledge and technical expertise to deliver impactful solutions for our clients.
Imagine a large faucet pouring water into a cup that has thousands of people drinking out of it simultaneously. The faucet represents centralized generation (coal, hydro, and nuclear plants that are typically owned by the utility). The thousands of people drinking the water represent the load (demand) for water (power) by customers. The utility is in the business of making sure the flow of the water going into the cup matches the flow leaving the cup at any point in time. Now imagine that a bunch of people want to add smaller faucets that also add water into the cup. This represents the idea of distributed generation (supply) being interconnected to the feeder (the cup). The ability for the cup to keep supplying water to the consumers, despite consumers adding more faucets, represents the cup’s hosting capacity: the theoretical limit of how much distributed generation a feeder can support. Understanding a feeder’s hosting capacity allows utility engineers to discern whether approving the next distributed generation system will push the associated feeder over the “upper limit” for what it can safely and reliably support. This is a core component of ConnectTheGridTM’s Technical Screening module.
The utility industry is currently in a state of flux around how to calculate this hosting capacity – the ability of the feeder to “host” distributed generation. To account for the possibility of the industry moving the needle with more advanced calculations, and to account for differences in calculations between utilities, West Monroe developed a robust and configurable way to calculate feeder hosting capacity. The team seeded the product with a calculation initially developed at the Illinois Institute of Technology’s (IIT) Center for Smart Grid Research and Technology (CSMART): a partnership between IIT, Commonwealth Edison, Silver Spring Networks, and West Monroe Partners dedicated to solving the issues affecting the electric grid, including the increased interconnection of renewable generation assets.
Putting it all Together
Figure 2 below illustrates this calculation in action: an engineer can analyze the hosting capacity for a specific feeder and overlay aggregate generation values as estimated by our theoretical output model. These values are aggregated for all systems currently interconnected to the grid (livened) as well as ones that are proposed and others that are already approved. This analysis tool allows an engineer to quickly scan a proposed system’s impact to the feeder by month of the year. When generation outpaces capacity, a further study into the system may be warranted.Figure 2: Aggregate Theoretical Distributed Generation Output vs. Feeder Hosting Capacity
On a personal note, I’ve been involved with this product’s vision, design, and development over the past few years and this was by far my favorite team experience to date. Regardless of title, role, and level, all of my colleagues were encouraged to think like product owners throughout the project. I believe that when team members understand and are proponents of the product’s vision, and when they’re guided with the right process and technical architecture in place, they perform at a much higher level. Additionally, we juggled the different technologies and functional use cases across our development team allowing us to keep things interesting and eliminate key-person risks. Overall, this team maintains an incredible sense of pride over the release of ConnectTheGridTM’s Technical Screening module and is excited to solve the next set of problems facing our utility clients.
1Pickering, Keith A. The Southern Limits of the Ancient Star Catalog and the Commentary of Hipparchos. DIO: The International Journal of Scientific History, Sept. 2002.