More manual on power generation

Sections on solar and wind.  Some rewording of the section on fuel-fired
generators.

manual.md

@@ -1061,12 +1061,13 @@ power generators
 
 ### fuel-fired generators ###
 
-Electrical energy can be generated at any voltage (LV, MV, or HV)
+The fiel-fired generators are electrical power generators that generate
-by fuel-fired generators.  These are all capable of burning any type
+power by the combustion of fuel.  Versions of them are available for
-of combustible fuel, such as coal.  They are relatively easy to build,
+all three voltages (LV, MV, and HV).  These are all capable of burning
-and so tend to be the first kind of generator used to power electrical
+any type of combustible fuel, such as coal.  They are relatively easy
-machines.  In this role they form an intermediate step between the
+to build, and so tend to be the first kind of generator used to power
-directly fuel-fired machines and a more mature electrical network
+electrical machines.  In this role they form an intermediate step between
+the directly fuel-fired machines and a more mature electrical network
 powered by means other than fuel combustion.  They are also, by virtue of
 simplicity and controllability, a useful fallback or peak load generator
 for electrical networks that normally use more sophisticated generators.
@@ -1088,6 +1089,25 @@ is needed to overcome the inefficiency of supply converters, so it is
 worth operating fuel-fired generators at a higher tier than the machines
 being powered.
 
+### solar generators ###
+
+The solar generators are electrical power generators that generate power
+from sunlight.  Versions of them are available for all three voltages
+(LV, MV, and HV).  There are four types in total, two LV and one each
+of MV and HV, forming a sequence of four tiers.  The higher-tier ones
+are each built mainly from three solar generators of the next tier down,
+and their outputs scale in rough accordance, tripling at each tier.
+
+To operate, an arrayed solar generator must be at elevation +1 or above
+and have a transparent block (typically air) immediately above it.
+It will generate power only when the block above is well lit during
+daylight hours.  It will generate more power at higher elevation,
+reaching maximum output at elevation +36 or higher when sunlit.  The small
+solar generator has similar rules with slightly different thresholds.
+These rules are an attempt to ensure that the generator will only operate
+from sunlight, but it is actually possible to fool them to some extent
+with light sources such as meselamps.
+
 ### hydro generator ###
 
 The hydro generator is an LV power generator that generates a small amount
@@ -1118,6 +1138,15 @@ water block adjacent to the geothermal generator.  This increases the
 generator's output, with the maximum output achieved with two adjacent
 blocks of each liquid.
 
+### wind generator ###
+
+The wind generator is an MV power generator that generates a moderate
+amount of energy from wind.  To operate, the generator must be placed
+atop a column of at least 20 wind mill frame blocks, and must be at
+an elevation of +30 or higher.  It generates more at higher elevation,
+reaching maximum output at elevation +50 or higher.  Its surroundings
+don't otherwise matter; it doesn't actually need to be in open air.
+
 administrative world anchor
 ---------------------------
 
@@ -1180,8 +1209,6 @@ subjects missing from this manual
 This manual needs to be extended with sections on:
 
 *   power generators
-    *   wind
-    *   solar
     *   nuclear
 *   powered tools
     *   tool charging