Controlling the Snow at Cardrona Ski Resort
Cardrona, a 20 minute drive from Wanaka in the South Island of New Zealand was made famous as a ski resort by being founded and built in 1980 by non-skiers who built a base area in the middle of the resort at 1670m – somewhat rare; it has New Zealand’s first international halfpipe and is also the home of the Cardrona Bra Fence! This controversial tourist attraction follows a tradition that at the bottom of the mountain, women left a bra on the Cardrona Bra Fence before leaving town and although some locals welcomed the fence others viewed it as an eyesore, embarrassment and potential hazard to distracted drivers. Attempts were made to see the fence removed but a local sheep farmer, John Lee - the unofficial guardian of the site - refused to remove the bras from the fence claiming it was the most photographed attraction in the area. But distracted we are because our visit to Cardrona was all about snow – and making sure there is enough of it to support a successful ski resort while maintaining the environmental status quo. In Cardrona the ski season starts in July and ends mid- September and aside from the Kiwis, it is a popular resort for Australians and many other nationalities.
In order to top up the natural snow Cardrona operates upward of 40 “snow guns” which draw water from a number of streams. Abstraction is permitted when the flow rate is adequate and this needs to be monitored by the resort which also needs to report the data to prove that they are operating within the terms of compliance set by the Otago Regional Council. Flow rate is measured with a Van Walt pressure sensor housed in an appropriately sized flume and wired to a vanwalt CONNECT telemetry system which collects the data, stores it on the web interface and from there it is forwarded by FTP to the Otago Regional Council. Additionally, the vanwalt CONNECT hardware is provided with internal relays which allows for the automatic switch of the enormous pumps which draw the water into the dedicated reservoirs. The relays are triggered based on alarm parameters. When the flow rate reaches a certain level the relay closes and when the rate decreases a second alarm is triggered and that opens the relay, breaking the pump circuit. The relay would then control the functionality of a snow generating device that turns the river water into snow in order to prepare the slopes in times of insufficient snowfall. Sounds easy? Yes, it is but a few challenges dictated some changes to the basic system:
• The (flat) tamper proof antenna which provides the GPRS signal proved to be the wrong choice because consecutive layers of snow dampened the signal. A “stick” type antenna is a little more vulnerable but solves the problem easily. • A solar panel keeps the battery topped up but in a mountainous region positioning of the equipment can be challenging. In the Southern Hemisphere a solar panel needs to point North but on this location a mountain shades the panel for a good portion of the day. Nonetheless we have a good amount of juice between 10 in the morning until 14:30 and so far this has been sufficient to keep the battery healthy. • Water freezes at 0*C and in the main the rapid flow has prevented the ice from forming in the flume stilling well but on one occasion so far we’ve seen that a layer of ice formed above the sensor and so therefore the readings were affected. We are attempting to find solutions. We will try some rock salt but if that fails then we will install a “bubbler” or perhaps even a small heating element. • The relay mechanism for achieving this system is controlled via a GSM network and utilises facilities to remotely control various data-logger options to perform functions such as hardware configurations, restarts and so on, plus a requirement to allow control of those relay switches and potentially open up even more options and possibilities.
The developments created for Cardrona, we believe operate as a true Internet of Things (IoT) system that doesn’t rely on any human intervention to control hardware. The software will sit and smartly monitor data and automatically respond to that data based on pre- defined rules, in this case monitoring water levels and turning off/on a snow cannon. The system was installed in early May and so far it has worked flawlessly. Occasionally there is a transmission delay around the 5pm mark which coincides with the skiers returning to base and hogging the network with uploads of photos of their adventures to Facebook or other social network sites. A second installation will be instated down-hill nearer the village of Cardrona and this will be used as a control point. There is also a plan to install this technology on some other streams to maximise water availability, because, in the end, snow is needed for skiing. What a contrast to the first season in 1980 when there was so much snow in the winter that the mountain was only able to open for 3 weeks as the remainder of the time was spent clearing the resort road with a bulldozer!
Vincent van Walt, Van Walt Ltd
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