A third kJ nd of disturbance to technical services is electromagnetic interference (EMI) with sensitive electrical systems such as aircraft electronic equipment, computers, satellite equipment, hearing aids, heart pacemakers etc. The DOE-environmental study identified 1400 systems in a special area which would be affected by a single power beam. 1.2.14 Rectenna Impacts (References: 76/6,77/1 8,78/1 ,7 8/3,7 8/41,7 8/68 .) 1.2.14.1 General This category summarises all impacts of the rectenna on the environment. 1.2.14.2 Waste Heat of the Rectenna The SPS-system is planned to deliver 5 GW electricity from each rectenna into the utility grid. The losses of a rectenna are reduced to the RF-DC conversion ( 89 %) and the grid interfacing ( 97 %). With these figures the overall rectenna losses, which will appear as waste heat, will be 790 MW. All SPS proponents compare this to conventional thermal powerplants, which produce waste heat of about 7500 MW to produce the same amount of electricity. The rectenna losses are distributed uniformly over the reception area of approx. 100 km . So the specific waste heat is about 8 W/m2. Experts do not believe, that this small amount of waste heat of the rectenna will affect the weather in that area. 1.2.14.3 Microwave Power Density beneath the Rectenna The rectenna is designed as a two plane receiver, with a metal-mesh ground plane as a RF-reflector and a foreplane with rectifying elements. It is calculated, that a maximum of 1 % of RF-power will pass through. So the land beneath the microwave receiver may be utilised similar to the area around the rectenna. 1.2.14.4 Land Requirements The land requirements for a rectenna are relatively high and depend mainly on the latitude of the reception site. Fig. 2.14.1 and fig. 2.14.2 present the required area as a function of latitude and longitude offset. A first NASA-study on rectenna site location considerations from 1976 points out, that for 120 rectennas proposed for the USA, 69 could be placed on land, the others had to be ^placed offshore because of lack of land availability. These land-based rectennas would require approx. 1/2 million people to be resettled. A more recent study defines exclusion areas in the USA, where rectennas should not be erected depending on certain conditions.
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