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Can ‘Smart ZNE’ address feeder hotspots?

I used to be a distribution grid planner in an era where utilities had a steadily growing customer base, and where grid planning and load shapes were predictable. This was before renewables started becoming more cost competitive, and traditional utility network planning, revenue models, and load management started facing the impacts of community- and customer-scale renewables.

Now we’re in an era where more cities and states are adopting higher renewable goals, presenting a Catch 22 situation for utilities: do nothing and risk losing part of their customer base; or start incorporating more renewables into the grid and prepare for significant changes to their traditional network planning and load balancing.

Either way, the electric grid as we’ve known it is changing. Making the grid ‘greener,’ and in the long run more reliable, is a lengthy process with many bumps in the road for both utilities and customers. Without strategic planning, a higher penetration of renewables will exacerbate distribution feeder hotspots and cause reliability issues, as well as change the traditional load profile of the grid. This can also impact the potential revenue streams for utilities to recover their necessary investments.

Many policies and green movements that are pushing for more renewables are also pushing for electrification (converting energy consumption from gas to electric), as part of the end goal of greenhouse gas reduction. This will further change the peak curve due to the newly added demand load from electric water heaters, electric vehicles, and any other appliances switched over.

For many of the same reasons that renewable energy is on the way to becoming cost-competitive with fossil fuels, zero net energy (ZNE) construction is also becoming more cost-effective according to NREL. As a result, ZNE continues to gain momentum. NBI’s ‘2018 Getting to Zero Status Update’ from earlier this year indicates that zero energy buildings have increased over 700% since 2012.

As a result, ZNE continues to gain momentum. NBI’s ‘2018 Getting to Zero Status Update’ from earlier this year indicates that zero energy buildings have increased over 700% since 2012.

‘Smart ZNE,’ or highly energy-efficient ZNE construction with intelligent grid-integrated controls, may become a major tool for utilities looking to address feeder hotspots and control their loads due to the increase in renewables. At least one utility, Southern California Edison, has already started testing this by partnering with a high-performance builder and studying the effects of newly built grid-integrated ZNE communities on their feeders.

There are similar untapped opportunities for utilities across the United States, including a growing number of builders and solar/storage distributers open to partnerships. By working with builders and developers, utilities can have an influence on development and address feeder issues before they may arise.

For utilities interested in setting up programs or pilots around this, the recipe to follow uses the main ingredients of ZNE design outlined below. In addition to grid benefits, offering incentives and design assistance for new construction also makes the utility’s service territory a more attractive location for developers, potentially increasing the utility’s customer base and revenue.

Start with a high-performance envelope

One of the core principles of zero net energy design strategies is a tight, high performance envelope. A major benefit of this is that it reduces the heating and cooling loads, and can even eliminate the need for central heating systems. Other architectural features such as building orientation and window placement also play a critical role in optimizing the building’s energy footprint, reducing the peak loads and overall energy draw, and hence the building’s grid impact. And not to mention improve the building owner’s comfort and health!

Focus on energy efficiency

There are many benefits to building in deep energy efficiency, as it reduces the overall project cost (by minimizing the amount of solar needed) and can also reduce the utility’s capital costs by offsetting the need to upgrade distribution equipment. Energy efficiency helps reduce the steep evening ramps, and minimizes how much the demand curve would be skewed by renewables. A smaller and more accurately sized PV panel also reduces the potential for generation backflow into the grid.

Make it smart

It’s much more cost-effective to design and build in demand response (DR) and control strategies during the new construction phase than add them later. These built-in controls enable customer-owned loads, energy storage, and renewable generation to directly communicate with the grid. This is a great pilot opportunity for utilities to test different control and DR strategies, as well as rate structure optimization.

Utilities can also train high-performance builders to include controllable grid-integrated devices such as grid-integrated water heaters, thermostats, batteries, and appliances such as clothes washers, refrigerators, and dishwashers. These devices and controls can help shift load to periods of peak generation, for example by pre-cooling freezers and the home.

Using basic ZNE strategies, combined with smart energy efficiency and storage, can be a much cheaper and quicker solution for utilities than updating the grid’s physical infrastructure, such as its wires and transformers. Though determining the most optimal rate structures and solar/storage control strategies will be unique to each utility and take some time to figure out, the result will be a more reliable grid.

These partnerships also enable utilities to cost-effectively build in demand response and other grid-benefitting capabilities directly into the future housing stock. This helps create a healthier and more comfortable future housing stock.

Interested in learning more about how DNV GL can support your ZNE efforts around building and program design, energy storage, or renewables?

Tiina Aardemae is a senior engineer with DNV GL, and has been working in energy efficiency and sustainability since 2009. Her experience includes technical strategy, new construction, energy efficiency program design and implementation, quality management systems, data management, and software product management. She is also a Quality Management Systems Auditor, LEED® Accredited Professional and a Certified Scrum Product Owner®. Prior to joining DNV GL, Ms. Aardemae worked as a distribution grid engineer and utility customer project manager. Outside of work, Ms. Aardemae enjoys trail running, eco-travel, and learning about passive house and zero net energy. To join Ms. Aardemae’s professional network on LinkedIn click here.



‘Grid Integration of Zero Net Energy Communities,’ by: Ram Narayanamurthy, Rachna Handa, Nick Tumilowicz, Electric Power Research Institute; C.R. Herro, Meritage Homes; Sunil Shah, Proclus Engineering LLC; 2016


‘Distribution Feeder Hotspots,’ by: Changfu Li, Elizabeth Ratnam, Jan Kleissl, Department of Mechanical and Aerospace Engineering, Center for Renewable Resource Integration and Center for Energy Research; 2016

‘Cost Control Strategies for Zero Energy Buildings;’ NREL; 2014


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