Manage Your Grid with Confidence

Jan 18, 2017

Many published surveys have identified large future increases in solar and wind distributed generation, both in North America and globally.  For solar, a report from the SolarPower Europe Association projects global solar capacity reaching nearly 400 GW by 2019 under a low scenario and over 500 GW under a high scenario.  That’s an increase of between 40% and 85% over current capacity.  This is due in part to decreasing solar prices, tax credits, net metering incentives, and other programs.  Currently for utility-scale solar in the United States, power purchase agreements are being signed for between 3 to 5 cents per kWh, comparing favorably to the average electricity price of about 10 cents per kWh.

Renewable wind energy shows similar trends.  The Global Wind Energy Council’s Global Wind Energy Outlook 2016 report forecasts global cumulative wind power capacity reaching between nearly 640 GW and 880 GW by 2020 under different comparative scenarios.  These equate to increases of approximately 50% to 100% over current capacity.  Under the scenario with the greatest increase, the resultant wind capacity by 2050 will be enough to satisfy over 36% of the global electricity demand.  The growth in wind generation can be attributed to reasons similar to solar: decreasing price of installation as well as incentive programs.

These truly impressive growth figures underscore the challenges posed as well as the benefits offered by solar and wind generation.

For benefits, it’s clear that renewables offer a clean source of power - reducing our carbon footprint - and also satisfy regulatory requirements like renewable portfolio standards that are also intended to decrease greenhouse gas emissions.  However there are other benefits as well, including providing a source of generation closer to consumption when located within distribution networks, reducing losses inherent in the transmission and distribution of power.  Use of renewables also provides utilities with an opportunity to provide additional services to customers in the form of new options for purchasing power from renewable resources, which is of interest to many customers.  This has been confirmed via many surveys, including one by Gallup in March 2016 which showed that in the USA, 73% of respondents prioritize alternative energy over traditional fossil fuel generation sources.

However the benefits of renewable energy are not without challenges.  One major challenge is the increased variability to power flow, voltage, and power quality created by renewables due to often frequent changes in solar irradiance and wind speed.  This can be mitigated to an extent via use of smart inverters for solar and energy storage systems, but these methods - especially the latter - can be very expensive.  Even with these methods in place, traditional generation sources must be kept available to provide power when the contribution from renewables decreases.  Another significant challenge is the potential reverse power flows which can occur on distribution feeders when load is low but generation from renewables - typically rooftop solar - is high.  This condition creates operational hazards for utilities as well as more complex protection schemes to manage the bidirectional power flows.

Fortunately, analytical applications and tools exist to forecast and help mitigate these challenges.  Distribution and transmission systems can be analyzed in realtime, near-term (hours or days ahead), or long-term (weeks to years ahead) to forecast and mitigate potential problems with variable renewable resources.  Utilities can examine changes to voltage, forward and reverse power flow, and unbalance - where one or more phases in a three phase system carry more load, leading to increased inefficiency.  Users can then study various scenarios to mitigate these variable conditions, through existing or planned smart inverters and energy storage options.  In addition, utilities can analyze how demand response and long-term energy efficiency programs can change loading conditions, or analyze the impacts of potential increases in electric vehicle charging stations.  Having the ability to analyze and plan for multiple aspects of grid operations from an energy and economic perspective - demand response, energy efficiency, distributed generation, energy storage, electric vehicle charging, and microgrids - gives utilities the information they need to improve safety, reliability, and efficiency as distribution networks change and evolve.

For more information on Nexant’s products and services that allow you to manage your grid with confidence, please visit our booth at DistribuTECH #3147 and online at nexant.com.