The World's #1 Renewable Energy Network for News, Information, and Companies.
Untitled Document

Predicting PV Plant Power Fluctuations and Optimising Energy Storage

The ability to accurately predict and prevent power fluctuations is of considerable importance to solar PV (photovoltaic) plant operators in terms of sustaining profitability, estimating revenue returns and ensuring customer quality of service. Variations in solar irradiance can cause rapid fluctuations in power generation, reducing the quality and reliability of the power generated by large grid-connected PV plants.

Such inconsistency in solar irradiance can be caused by a number of factors, including shadowing as a result of cloud cover and dust gathering on PV panels. For intervals of less than ten minutes, these fluctuations are directly absorbed by PV electricity systems which results in variations in power frequency. Utility operators are powerless to correct these imbalances which can ultimately result in electrical power systems failure.

Battery Storage Systems

Typically, PV power fluctuations are counter-balanced by the use of battery storage systems within conventional PV power plants. However, battery systems not only increase the size and cost of PV power systems but power fluctuations also have the effect of reducing the useful life-time of the battery storage system. 

Simple Moving Average Method

A new and effective technique combining a PV energy storage system with a novel smoothing strategy known as the Single Moving Average (SMA) has been proven to not only reduce PV power fluctuations but also optimise battery storage systems by reducing their usage within PV power plants.

This approach calculates the SMA of past PV energy production over a certain time period — the longer the running average, the smoother the PV Power fluctuations. The key advantage of this technique is that the battery state of charge (SOC) will always return to its initial condition and therefore does not need a specific control. This means decisions do not need to be made about when to conserve power to avoid shortages, but more importantly it helps avoid damage to the battery bank, prolonging the useful life of the battery. 

It also calculates the SMA even on clear days when irradiance is not a factor in order to measure a longer and more complete operating period. This is done to ensure that the maximum possible power fluctuation is below PV plant operator requirements. Combined with an empirical technique, as discussed in the next section, this process enables the prediction of PV power fluctuation on a day-ahead basis. The use of the battery storage system can therefore be fully optimised, minimising storage requirements.

Optimising Battery Storage

The SMA technique has been evaluated over a twelve-month period on 5-s registered power output from a 1.1-MW PV plant operated by Acciona Energy in Tuleda, Spain. Given the normal operating characteristics of the plant, the energy storage requirement for smoothing maximum power fluctuations below 2.5 percent per minute was calculated. Simulated over an annual period, it was determined that 2,400 seconds of storage per day was required in order to reduce the power fluctuations. This level of power storage was to be applied every day regardless of weather conditions in order to ensure the required level of power fluctuation smoothing while optimising battery storage requirements. In terms of battery storage capacity, this translates into 312 kWh per annum.

Acciona Energy PV Plant in Tudela, Spain where the Single Moving Average (SMA) Technique was evaluated. Images are subject to copyright. 

Mitigating Predictive Uncertainty

The degree of predictive uncertainty was also measured and was found to have a positive correlation with the minimum daily energy storage required to reduce PV power fluctuations below 2.5 percent per minute over this period. This means that the storage time required could be accurately scheduled one day in advance to minimise the use of the energy storage system. In extraordinary situations, where greater than predicted PV fluctuations are unavoidable, a ramp rate limiter can be used to smooth power fluctuations.

Conclusion

The SMA smoothing technique has been simulated over a one-year period and has proven to be an effective means of decreasing power fluctuations in large PV plants. Importantly, its predictive accuracy has demonstrated an ability to optimise the usage of energy storage systems over a prolonged time period. During its evaluation period, the technique was shown to reduce average PV energy storage requirements by more than 15 percent, requiring less than 263 kWh capacity of an average PV battery storage system per annum.

Untitled Document

RELATED ARTICLES

Global Renewable Energy Roundup: China, Kenya, Turkey, India Seeking More Renewables

Bloomberg News Editors China is being encouraged by three industry groups to double the nation’s solar-power goal for 2020 to make up for sh...

Why Smarter Grids Demand Smarter Communications Networks

Mark Madden

Historically, utility networks and communications networks have had little in common.

Don’t Like Obama’s Clean Power Plan? Fine, Here’s Cap and Trade

Mark Drajem and Lynn Doan, Bloomberg Republican governors who boycott the Obama administration’s new power-plant regulations may instead get an offer they...

Vehicle to Grid Energy Storage Experiment Underway in California

Dana Hull, Bloomberg In a new pilot program, a California utility is paying drivers of BMW electric cars to delay charging their vehicles ...

PRESS RELEASES

Array Technologies’ DuraTrack HZ v3 Continues to (R)evolutionize at SPI

Array Technologies, Inc. (ATI) prepares to showcase its recently launched tracking syst...

Appalachian's Energy Center assists counties with landfill gas to energy projects

The Appalachian Energy Center at Appalachian State University recently completed a proj...

Early Bird Registration Deadline for GRC Annual Meeting is This Week

The deadline for early-bird rates for registration for the biggest annual geothermal ev...

Redesigned HydroWorld.com Video Gallery

Hydropower news and information, and interesting promotional announcements are now avai...

FEATURED BLOGS

Transitioning to Net-Zero Living

Judith and Jeffrey adore living in Belfast, Maine – a quaint harbor town of Belfast, Maine. They previously res...

The True Cost of Electric Vehicles in Australia

In order to avoid increased congestion, further greenhouse warming and lessen Australia’s reliance on imported ...

The Coming Multi-trillion Dollar Energy Investment Drive

In coming years, a multi-trillion dollar low-emission energy investment drive will get underway. Three catalysts wil...

The Perfect Elevator Pitch

The elevator pitch is a concise statement that grabs attention and communicates value, ideally leading to a next step...

FINANCIAL NEWS

Javier Marcos was born in Pamplona, Spain, in 1983 and is a member of the PVCROPS Project team. Javier holds a M.Sc. degree in Industrial Engineering from the Public University of Navarra, Pamplona, Spain. In 2011, Javier received his Ph.D. in ind...

CURRENT MAGAZINE ISSUE

Volume 18, Issue 4
1507REW_C11

STAY CONNECTED

To register for our free
e-Newsletters, subscribe today:

SOCIAL ACTIVITY

Tweet the Editors! @jennrunyon

FEATURED PARTNERS



EVENTS

Intersolar North America 2016

Exhibition: July 12 - 14, 2016; Conference: July 11 - 13, 2016 Intersola...

Intersolar South America 2015

Exhibition and Conference: September 1-3, 2015 Intersolar South America ...

Intersolar Europe 2016

Exhibition: June 22-24, 2016; Conference: June 21-22, 2016 Intersolar Eu...

COMPANY BLOGS

Less Is More

When you’re giving a presentation, one of the easiest things to do...

Captivology

One of the biggest challenges we face as efficiency sales professionals ...

How To Optimize Your Meeting Schedule

Do you spend more time in meetings than you do actually working? While m...

NEWSLETTERS

Renewable Energy: Subscribe Now

Solar Energy: Subscribe Now

Wind Energy: Subscribe Now

Geothermal Energy: Subscribe Now

Bioenergy: Subscribe Now  

 

FEATURED PARTNERS