Solar power forecasting in Vietnam made easy

27 March 2020

Vietnam keywords: In this post you'll learn about:

  • Tiềm năng năng lượng quang điện
  • Bức xạ mặt trời
  • Chiếu xạ ngang toàn cầu
  • Chiếu xạ ngang toàn cầu

Looking for solar radiation maps?

You can find our latest solar radiation maps for Vietnam here.

Solar energy in Vietnam

Solar power has been growing exponentially in Vietnam. As a result, the Vietnam power system is undergoing a significant change, driven by the integration of many tens of thousands of rooftop solar PV systems and a large number of utility scale solar farm sites. As of the middle of 2019, 4.4GW of large scale solar was connected to the electricity grid.

Challenges include grid congestion, overload and frequency oscillation. For example, EVN has already communicated that the regions of Ninh Thuan, Binh Thuan and Dak Lak have already experienced the overloading of 110kV and 220kV transmission lines.

Vietnam Transmission Network Solar Forecasting.png Image Credit: EVN NLDC

At present, there is sufficient flexible generation from the nearly 22GW of hydropower installed in the country to manage this (project to grow to nearly 28GWp by 2030), but battery storage systems are also being considered to help offset solar intermittency.

Solar radiation resource in Vietnam

The available solar resource in Vietnam is very high. Annual solar irradiation can exceed 1400 kWh per square metre in the north and over 2100 kWh per square meter in the south. Clouds are the dominant driver of solar production variability, and is mostly driven by convective clouds (i.e. thunderstorms).

solar-resource-assessment-vietnam.jpg Map of solar irradiance over Vietnam at midday on 25th March 2020, showing impacts of clouds on the available solar resource.

The importance of solar power forecasting in Vietnam

EVN NLDC has recently commented on the challenges of solar intermittency:

“Despite the fact that solar power is a valuable capacity addition to the power system which is facing difficulties in power supplies, a large number of solar power plants coming into operation in a short period have been causing many challenges to the operation of [the] power system. This situation is caused by the intermittency and dependence on weather conditions of this energy type” Source

Solar Power Forecasting is essential for successful grid integration of increasing amounts of renewable energy. Accurate forecasts can help with day-ahead bidding of power, by allowing larger bids and/or reducing imbalance or accuracy penalties. Accurate solar forecasts are also helpful intra-day, for forecast revisions or re-bids by solar asset operators, and for system operators for balancing purposes including the minimisation of plant curtailments.

Deputy Director of the EVN NLDC, Mr. Vu Xuan Khu, recently commented on the importance of this topic, saying:

“According to the statistics on solar power projects under operation, just in about 5 to 10 minutes, the plant’s generation capacity can vary from 60-80%. The fluctuations occur randomly based subject to the weather. It should be noted that solar power plants in a same area often have fluctuations in generation capacity at the same time.”

Solar forecasting methods best suited for Vietnam

While Mr. Khu is right about solar variability, we disagree that it is random. In fact, it completely possible to predict cloud events and their impact on solar generation.

For solar asset owners and operators, there are two common approaches to establishing solar power forecasting.

The first is to subscribe to a solar power forecasting service completely made by a vendor. This approach works well provided that plant specifications are well described, and the power curves can be optimised via machine learning approaches (e.g. "Tuning" as carried out by Solcast).

The second approach is to subscribe to a solar radiation and weather forecasting service, and use internal capabilities to build the conversions from radiation to power. This approach can be successful, but requires strong internal capabilities, since the conversions from radiation to power are highly non-linear and the plant and weather condition impacts are numerous.

Matching solar forecasting capability in Vietnam with the market

It is expected that from 2021, the competitive electricity retail market will be put into 'pilot operation', then, and from this point, the operation of the power system and electricity market will be 'much different and more difficult' according to the NLDC.

Vietnam Market Bidding Solar Forecasting.png

For merchant solar power plants which sell energy on the open market (known as the “day-ahead” and “hour-ahead” markets), solar power forecasting becomes very important at an individual farm level.

For these solar farms, solar energy is sold a fluctuating rate rather than at a fixed tariff, and the bidder must be very confident in the level of energy they can guarantee to provide.

Solar forecasting requirements for Vietnam

For Vietnamese solar farms, there are 3x forecasting horizons of great importance:

  • Week Ahead Planning (WAP) predictions
  • Day-ahead forecasts
  • 1-hour ahead forecasts

Solcast have built our technologies around these requirements, and can offer 0 to 7 day ahead forecasts (từ thời điểm hiện tại tới 7 ngày tiếp theo) for your solar farm.

Solcast allows you to create your own solar power forecast

Solcast allows asset owners or operators to add their own solar plants to the Solcast system using their web browser, and instantly start using and evaluating forecasts. The process takes only a few minutes and requires no credit card. Forecasts can be downloaded to CSV for analysis, and recent forecast accuracy over the site can be displayed on a graph. When the forecast goes into operations, a credit card is required for monthly subscription fees, and the Solcast API makes integration and submission of forecasts easy to automate.

vietnam-solar-farm-API-toolkit.png The above is an example of a Vietnamese utility scale solar farm setup for forecasting in the Solcast API Toolkit.

Solcast also provides live and forecast solar irradiance data as input to your own power forecasting methods

Solcast also provides direct access to solar irradiance data via API. Users can learn how to access these data using their web browser, where they can download sample data and begin evaluating forecasts. Forecasts can be downloaded to CSV, JSON or XML for analysis.

Are you a solar farm owner or operator in Vietnam?

Solcast has made it very easy for Vietnamese solar farm operators to access high quality solar power forecasting data. Everyone who creates an API Toolkit account can create their own utility scale solar farm forecast and try it for free. If you have access to PV Power measurement data, you can upload it in the API Toolkit to further improve the forecast.

Learn More:

Dr. Nick Engerer

Dr. Nick Engerer

Solcast Co-founder • Author

Nick is an expert in the field of solar radiation and distributed solar PV modelling, and has co-founded Solcast out of a sincere desire to enable others to build the solar-powered future.

Read more about Dr. Engerer's scientific papers

Solar Power Forecasting