Stadia and training grounds are increasingly subjected to extreme weather conditions, either forecast or unexpected. Weather patterns are no longer 'patterns' by definition, as unseasonable poor weather has been the cause of not only lost training opportunities but also lost fixtures and, subsequently, lost revenues.
There are a variety of cover systems on the market and they can be reasonably grouped into three categories.
Where the cover is 'over' the pitch and allows groundsmen to work with six feet or more of clearance, as well as protecting the playing surface from rain and snow. Combined with warm air blowers, the raised tent helps protect the pitch against freezing temperatures.
Here, the cover rolls across the pitch, in direct contact with the grass, providing an insulating effect.
Deployment can be manual, usually side to side, or automatic where the rollers travel from goal to goal. This is generally because of the weight and effort and power required to move the covers.
Many different ideas have emerged over the last decade. For example, rectangular frost covers that need to be manually dragged into position and pegged with easy to identify pegs (count them out, count them in) to avoid damage later to mowers or footballers in full flight.
Hovercovers and framed covers for cricket squares and bowlers' run-ups have been important accessories. Cricket, in particular, offers an interesting challenge because of the field shape. When the outfield is saturated from a thunderstorm. the match can still be unplayable even if the square and bowlers' run-ups have been protected.
Eden Gardens in Kolkata are looking at ways the entire round shaped field could be covered to send heavy rain into the storm drains, and play continue once the heavy showers have passed.
Polo grounds are also being punished by extreme rainy conditions and the challenge is the size of area to be covered economically, a staggering 10 acres; equivalent to nine football fields.
Automated Motorised Rollers or Manual Air Rollers?
Speed of deployment and ease of handling versus cost. The ability to cover a pitch within forty-five minutes and, as importantly, to uncover the pitch in the same time, requires a motorised roller. The rollers have motors in each end and operated by remote control, it's like controlling a roll of high-tech carpet. However, these rollers are a fixed item and become an intrinsic part of the stadium or training ground infrastructure.
Soil Moisture Content
We know good drainage is key to a good playing surface, however, not all pitches have 'good drainage' or drainage that can cope with torrential rain over a prolonged period. Too much water within the soil will lead to saturation and there will be standing water. Playing on such a surface will damage the turf, leading to costly reparations and be physically dangerous for the players.
Obviously the use of SubAir systems will draw the excess water through the pitch into the drainage system, which is fine for a major stadium construction, but a little on the expensive side for a training ground complex.
In conjunction with accurate internet forecasting, an automated roller can be quickly deployed prior to heavy rain or unwanted rain, and removed once the storm or squall has passed on. The waterproof material in the covers ensures the pitch is available for use in its best presentation at the time the team manager or coach requires it, despite the weather.
By far the biggest demand for pitch covering systems is when the frost and snowfall becomes severe enough to freeze the soil or snow covers the ground entirely. Raised tents and air rollers need a small team of skilled operators and have been proven over many years. One huge benefit is that they are transportable, albeit with some medium weight lifting gear required. Tried and tested tent structures and air rollers have offered a lower cost solution as, when not in use, they can be stored off site.
As we move into soil temperature control, it's a good idea to acknowledge the many different types of pitch. For example, a pitch without undersoil heating can be protected with a cover plus warm air blowers. A pitch with undersoil heating can use a cover that utilises the insulating effect. A stadium with abnormal sunlight, due to architectural design, can benefit from covers that split to protect the side of the pitch not receiving sunlight. It is remarkable that even some of the most recently built stadiums in 2013 have designs preventing sunlight reaching the playing surface for five months or more of the year.
Soil Temperature Control
The properties of the cover materials, when deployed naturally, insulate the turf to protect from temperatures down to minus 4OC. In the absence of undersoil heating, this is a valuable additional tool for the groundsmen. The solution that cover manufacturers aim for is to keep a playing surface entirely free of snow and snow damage. Tractors with brushes can be used to brush away snow from the covers just before they are rolled back to storage, presenting a perfect pitch.
At present, many clubs with undersoil heating are using it to disperse snow and frost from the playing surface. Effectively, the undersoil heating sends warmth to the surface to melt the snow and for the snow melt to drain away as rain would. Our studies discovered this was indeed like having your central heating on at home, but no roof. The cost to maintain the warmth to keep the pitch snow or frost free becomes exceptional and, in this day and age of concern for the environment, unacceptable.
To expand on the above theory, leading football industry environmentalists, Mike and Julia Goodfellow-Smith of Quest for Future Solutions, have entered the debate, analysing detailed weather data from the last ten years (see below). It was discovered the insulating properties of the pitch cover, in conjunction with undersoil heating, reduced fuel costs by 70%, therefore reducing carbon emissions by a remarkable 70% as well.
The benefits of this research and development of pitch covering products and their applications led to more surprising results, one of particular interest to groundsmen and stadium managers in cold climate locations was germination.
Pitch covers are simply another tool at your disposal, the illustration above shows grass being cut in the foreground and lighting rigs working through the cover in the background, combining with the insulating properties.
There is strong evidence that pitch covering systems are now a part of the future in stadium and training ground construction and pitch maintenance.
Where super-efficient drainage solved one set of problems, it partly led to watering the pitch to maintain a balance of soil, air and water to avoid wilting point becoming commonplace. Water is getting expensive, too.
High powered undersoil heating serves a very good purpose and is a valuable part of the professional playing surface delivery, and pitch covers can easily reduce the cost of operating this fine invention.
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The effect of pitch covers on a sample pitch using Met Office data
Our sample pitch currently uses undersoil heating at stage 1 when air temperature is due to drop from 4OC to minus 4.5OC. Stage 2 is used from minus 4.5OC to minus 6OC.
Based on minimum daily temperatures provided to Quest for Nottingham from 1/1/03 - 31/12/13, from which we have taken ten year averages.
With the pitch cover in place, undersoil heating would be used at stage 1 from 0OC to minus 6OC , and stage 2 when air temperatures are due to drop below minus 6OC.
Impact of Pitch Cover
Based on these data and assumptions, the following can be ascertained:
Without Pitch Cover:
No of days p.a. on average at stage 1 - 102
No of days p.a. on average at stage 2 - 3
Litres of oil p.a. for one pitch - 86,120
With Pitch Cover:
No of days p.a. on average at stage 1 - 32
No of days p.a. on average at stage 2 - 1
Litres of oil p.a. for one pitch = 27,170
Average no of days that temp fell below 4OC - 105
Average no of days that temp fell below 2OC - 63
Average no of days that temp fell below zero - 33
Average no of days that temp fell below minus 2OC - 13
Average no of days that temp fellbelow minus 4.5OC - 3
Average no of days that temp fellbelow minus 6OC - 1
kg CO2e per litre of gas oil - 3.6028
No of litres of oil used per day -one pitch - stage 1 - 800
No of litres of oil used per day - one pitch - stage 2 - 1,500
Litres of oil saved p.a. for one pitch with cover - 58,950
Percentage reduction in oil use - 68%
kg CO2e saved p.a. for one pitch with cover - 212,385
Julia Goodfellow-Smith, Quest for Future Solutions,
19 January 2013