Remote Sensing: The Secret Weapon of Wind Prospecting (Part 2)
Why You Need To Measure
Prospecting involves an initial look at likely sites in a given region to see if they meet the five criteria outlined above. Mesoscale wind maps and site-specific historical wind data, such as data from met stations at nearby airports, are typically the first thing the developer consults.
Mesoscale wind maps and historical wind data have limitations in prospecting a wind site. In some regions of the world, these sources of data do not exist or exist in much less detail than is desirable. Even where these data sources do exist, they have uncertainty built in.
A mesoscale wind map is built using modelling and extrapolations. The site-specific topographic characteristics -- such as local elevation and surface roughness -- may differ from that assumed by the map. And many such maps are developed using data measured only up to 50 or 60 meters high. This introduces uncertainty about the wind speeds at higher height and the wind shear.
Historical wind data may have been captured over a longer time and measurements may have been taken closer to the site, but measurements usually have only been made to 30 meters. There is no substitute for a new measurement campaign to capture as much wind data from the geographic location of the proposed wind farm as possible.
Don't Delay
Getting enough data to make decisions as quickly as possible allows the developer to cut losses and begin development more rapidly on promising sites. Before the commercialization of remote sensing systems, wind measurement meant putting up a tilt-up tower. Permitting, procuring, and installing met towers can add months to a prospecting cycle. When you consider the cumulative costs per site -- which can run hundreds of thousands of dollars per year -- it's easy to see the advantages of a remote sensing system that needs no permitting and can be deployed and transmitting data in one day. It is also important to have a system in place for communicating and rapidly understanding the data so that you can make decisions as soon as you have enough data to make them.
Confidentiality
Compared to a met tower with its high visibility and public permitting process, remote sensing systems attract very little attention and can usually be deployed without compromising the confidentiality of your wind project. Keeping the details of the proposed project private until the right time can save the developer time, money, and energy.
Using the Wind Data Beyond the Prospecting Stage . . . Project Finance
Tower data may be required as part of the wind resource assessment report for a project financing proposal. When remote sensing data such as data from Triton, Second Wind's advanced sodar system, are included, some analysts prefer that the remote sensing system be "validated" by measuring concurrently with a tower for a certain period of time.
Second Wind's customers typically deploy Tritons for a few months and use the Triton data to disqualify sites that are not suitable. If the site qualifies for further study, a met tower may be erected after several months next to the already running Triton. In what we call "reverse validation," a good correlation between the met tower and Triton can be used to validate the Triton data that was gathered before the met tower was put up. If the wind resource at the site does not pan out, the developer has saved the cost of putting up a met tower and can inexpensively move the Triton to the next site.
Back in the Black
To date, remote sensing systems have been primarily used in wind resource assessment applications. However, the flexibility, low profile, and re-usability of remote sensing systems helps wind developers save many months and thousands of dollars before the wind resource assessment even begins. Using remote sensing systems in greenfield prospecting can help keep your project out of the red.
