Sentinel-2 satellite maps: because we value up-to-date information
- Best practices
- J. Beták
- Oct 21, 2020
- Comments
Satellite maps are a basic tool for decision makers, planners and developers of photovoltaic (PV) power plants. They are essential for site-selection, land evaluation and understanding the local topography. They play an indispensable role, especially for the evaluation of sites in unknown territories and in peculiar climate zones.
The Sentinel-2 satellite mission is celebrating its fifth anniversary (having launched in June 2015). How does this image data help the solar energy community and what is its potential?
It has been more than 15 years since global satellite maps emerged in the online world, freely accessible to everyone. First, these were just blurry pictures of the landscape, but these were gradually replaced with higher resolution images of cities, followed by suburban zones and remote areas. Suddenly, we could spot streets, houses, and even our parked cars. Accessibility of satellite maps changed the perspective of the world in many domains, regardless of our preference for Google Maps, Bing Maps, Baidu Maps, HERE maps or any other provider.
Today, the frequency of imagery updates varies considerably across providers and also differs by region. Some countries are regularly updated in their entirety almost every year, whilst in some regions, urbanized areas take preference. But updates for large parts of the world are still only occasional – and some imagery of remote areas might be more than a decade old.
This may be land where the recent growth of utility-scale photovoltaic (PV) power plants has been incredibly fast (see illustrative images at the bottom). For solar decision-makers, the issue here is that the satellite imagery seen on popular map services often does not reflect these radical changes.
As a fast-moving industry, we need a widely available resource that can account for this pace of change to support effective planning – particularly as we bring online some of the largest sites ever built in remote regions of the Middle East and Asia. Sentinel-2 has the potential to provide such a resource.
Operational satellite programmes
High resolution satellite imagery has been developing fast and it does a pretty good job. To a large extent, it has become a private business, thus it naturally focuses on domains where sustainable profit is achievable.
In the shadow of these imagery providers, we have operational satellite programmes run by national or international organizations. These programmes often focus on environmental monitoring and provide enormous data inputs, amongst other things, to understand both the present landscape and current climate.
The Sentinel 2 mission
We emphasize, among others, the Copernicus Sentinel-2 mission; a collaborative project administered by the European Space Agency (ESA). Sentinel-2 satellites carry multispectral instruments, which provide imagery in 13 spectral bands, covering both the visible and infrared parts of the spectrum. The pixel size in the visible spectrum is 10 meters. This means that Sentinel-2 cannot identify objects such as individual cars or trees. But it is detailed enough to identify larger buildings, roads, smaller PV power plants, and certainly large PV power plants.
Nowadays, two of these satellites are in orbit (almost 15 times a day) at an altitude of 786 kilometers, scanning the Earth’s surface. The revisit time is 5 days; in other words, every part of the Earth’s surface between the parallels 84°N and 56°S is scanned at least once every five days (around the Equator this is approximately every three days). This scanning frequency brings great advantages.
The launch of the first Sentinel-2 took place in Jun 2015. Thus far the mission has provided a full five years of continuous time-series imagery. In addition to this, ESA provides ready-to-use imagery products, which can be downloaded and used immediately from its vast data pool, adopting a full, open and free-of-charge data access policy.
Case studies: Large-scale PV development in remote regions
Looking at some of the new ‘megaprojects’ coming online in remote regions worldwide, it is clear to see just how quickly these sites increase in scale.
1. Solar park near Bhadla (Rajasthan, India)
- Presently the largest PV power farm in the world, with an installed capacity exceeding 2.25 GWp
- Expanded from an area of ca. 1 square kilometre in 2015 to ca. 45 square kilometres in 2020
- Numerous developers have been involved
- Solargis delivered data and consultancy services for several projects, located in this area
We are proud to be associated with the development and operation of this solar park. This began back in 2011, when our colleagues had the chance to visit the Bhadla Solar Park. At that time there was nothing there but barren land. Over the next few years we supported multiple solar developers to accurately estimate the long-term solar resource at Bhadla for their bid preparation. Recently, we have been able to support solar power plant owners with performance evaluation and intra-day forecasts for their operational projects.
2. Benban solar park near Kom Ombo (Egypt)
- Largest PV power plant in Africa, with an installed capacity exceeding 1.65 GWp
- Constructed in the space of a few months (see the timeline imagery)
This is another project where we have been supporting multiple customers across different project stages - from feasibility to operation. Since 2015, we have delivered bankable resource assessment studies for this project to multiple customers, and recently we have been supporting some customers with reliable performance monitoring and short-term forecasting of solar power.
How can I take advantage of Sentinel-2 data?
The Sentinel-2 satellite program creates a unique archive of images from recent history, making it possible to witness the rapid growth of PV power plants. Using recent images is an important method for project planners and developers to understand the most up-to-date developments in a region of interest, and to plan for future expansion.
Solargis is working on regularly processing these up-to-date images, with the aim of extracting value and supporting agile decision making for investors. Our consultancy activities already benefit from Sentinel-2 data, as we are able to illustrate the impact of current changes to land use and topography on future projects.
To make this resource more widely accessible to Solargis users, in future we plan to implement this data set into Solargis Prospect, our online app supporting development of solar projects in the stage of site selection and prefeasibility assessment.