Bibliography, Scientific references
ABSTRACT: Roof-Spray cooling systems are being extensively used to reduce the air-conditioning usage in industrial and commercial buildings. In buildings without air-conditioning, evaporative roof spray cooling systems help to reduce the interior heat.
   - Co-Authors: A. Carrasco, R. Pittard, S. N. Kondepudi · S. Somasundaram
ABSTRACT: Evaporative cooling technologies such as mist spraying, sprinkling of roofs, and water spraying onto air-conditioner outdoor units were taken up as environment measures for an investigative study. Demonstrative experiments confirmed that mist spraying at windows and roof-top water sprinkling have a remarkable effect of reducing the inside temperatures of the building. The experiments confirmed also that all of the evaporative cooling technologies used have an energy consumption reducing effect.The calculation made it clear that mist spraying is particularly effective as a heat-island countermeasure and water spraying onto air-conditioner outdoor units for businesspurpose buildings is so as an energy-saving countermeasure.
   - Co-Authors: Yoichiro KITANO, Naoya NAKAGAWA, Reiko MIYOSHI*and Koji TOYOSHIMa - Planning Department of Osaka Municipal Waterworks Bureau, JAPAN

Note: Comprehensive Japanese research. The calculation made it clear that mist spraying is "particularly effective" - inspite of the fact, that Osaka is located in the humid subtropical climate zone, and authors describe their roof-top water sprinkling system as an American-type one, controlled merely by a simple time-scheme: "a water sprinkling cycle was structured that consists of 15 seconds of water sprinkling and seven minutes of stopping". These two circumstances are responsible for the relatively poor effects, reducing roof temperatures by mere 15 oC (from 60-62 oC to 45-47) compared to the 30-45 oC reduction of our "Water-film Technology" (from 65-75 oC to 28-32 !)
ABSTRACT: Four sustainable alternative-energy cooling system options are investigated to quantify the actual energy that may be saved when employed in conjunction with conventional air conditioning systems. The four systems considered are active mass cooling, night flushing, roof-spraying and a roof-pond. The roof-spray system showed the most effective results in limiting heat gains to the one-room building and keeping peak room temperatures low.
   - Co-Authors: Jaco Vorster; Robert Dobson - Department of Mechanical & Mechatronic Engineering, University of Stellenbosch, South Africa
ABSTRACT: A simplified mathematical technique is presented with which preliminary evaluation of the effects of roof spray evaporative cooling can be made. This method incorporates the effects of solar flux, ambient temperature and the humidity of the environment.
„solar absorption of a water layer relies on the water depth and its incidence angle. However, the dependence of solar absorption of a water layer on the solar incidence angle and the water depth had not been taken into consideration in the simulation models proposed in the past”
   - Author: Sekhar Kondepudi
ABSTRACT: Currently, roof-spray systems are achieving greater effectiveness due to the availability of direct digital controls. The objective of this thesis was to develop a mathematical model of the heat transfer through a roof-spray cooled roof that predicted heat transfer based on existing weather data and roof heat transfer characteristics as described by the Transfer Function Method.
   - Author: Joseph A. Clements
ABSTRACT: In this paper the main stress is given on energy conservation by using technique of Roof surface evaporative cooling for Air-conditioning system. The target of saving and conserving energy up to 15 to 22% but in this case we achieved our goal of energy saving up to 13% by adopting RSEC technique – covering the roof with water absorptive and retentive materials such as gunny bags, brick ballast, sintered fly-ash, coconut husk or coir matting - must be kept wet throughout the day using a water sprayer. On account of their porosity, these materials when wet, behave like a free water surface.
   - Co-Authors: R.B. Lokapure, J.D.Joshi, Shivaji University Kolhapur, India

Note: 13 % of reduction is still achieved – in spite of the primitive technology, and of the fact that summer climate in Kolhapur is comparatively cooler, but much more humid, than neighbouring cities in India.
ABSTRACT: How Can Roof Cooling Save Energy? What can this reduction in cooling load mean for your facility? What’s This Going To Cost? Look at an example to demonstrate cost savings and return on investment: A payback period of this length is well below the 3-3.5 year industry standard for an energy conservation system.
   A control scheme (either software or programmable control box) activates each zone for a period of 15-20 seconds, spraying the aforementioned thin film of water. Once all zones have been adequately sprayed, a “dwell time” of 2-3 minutes is allowed for evaporation to take place. The cycle then begins anew. This entire sequence is usually monitored by a thermostat.
   - Author: John D. Strait 

Note: Though the text seems to be a thinly disguised advertisement, it recovers the weeknesses of even the best American systems. They are controlled merely by a pre-set „scheme” or simple temperature-based feedback – though real EVAPORATION is much more influenced by relative humidity, air-movement, and quite a few other, weather-depending and ever-changing circumstances. So in most of the times the roof-surface is either fully WET, needing „dwell time”, or it could be totally dry for almost full cycles of all zones. That’s why they can only make 0,1gal/ft 2/day = 4,2 liter / m 2 /day to evaporate – compared to the values of 10-15 liter / m 2 / day of our system. Evaporation of 4,2 l/m 2/day (assuming that there is no run-away-water loss at all - though that seems quite unrealistic int he case of this type of „controll”) means less than 2.700 Wh / day / m 2 of heat carried away. That is less than 1/2 of the Solar heat load – and 1/3 of the cooling effect of our „Water-film Technology”.
ABSTRACT: THEORY VS. PRACTICE IN DIRECT EVAPORATIVE ROOF SPRAY COOLING. This paper will examine in depth the development of roof spray cooling int he US and elsewhere, the theory and practice of roof cooling, and the limits of system application.
   The impact of roofing construction , building location, and internal and external load on the effectiveness of roof cooling are considered. Also discussed the theoretical and actual effect of roof cooling on a facility's energy consumption, and on internal temperature variations where there is no mechanical airconditioning.
   A complete survey of most studies and findings to date are presented. Guidelines for considerations of roof spray cooling systems are developed, incorporating ASHRAE methodology.
   In order to calculate the heat gain / cooling load that the roof contributes to a facility, the1981 ASHRAE Fundamentals Handbook is employed.
   - Co-Authors: J. L. Smith, M.E., P.E., Florence, AL et J. Carey Smith, Atlanta, GA
ABSTRACT: there is little reference  data concerning the design or control of such systems. In order to propose a method for designing and  predicting the performance of a water mist system, we discuss differences in cooling effects in the  context of particle size distribution of water mist. The results of numerical fluid analysis showed there is no significant difference in temperature reduction for different particle sizes.
   - Co-Authors
Hideki Yamada, Gyuyoug Yoon, Masaya Okumiya, Hiroyasu Okuyama -  Graduate School of Environmental Studies, Nagoya University; Institute of Technology, Tokyo, JAPAN