Neigbourhood Solar Steam and Heat
Solar Thermal Power can be gained from south facing walls and flat roofs in urban areas. Because most energy in homes is used for heating and cooling it makes more sense to go solar thermal than solar photovoltaic. If it is done one neighborhood at a time if can mean a c-change in energy consumption, probably outperforming efficiency measures (which are still not carbon neutral).
Flat roofs and southfacing walls could provide most if not all power needed
This is one of the ideas carried with www.parabolictrough.org. Because it is a process akin to installing gas or water, but as some tubes etc. can be run over the roofs it is much less invasive. It does require organization within a neighborhood and some investement. Key elements are:
Thermal Solar Capture
Using parabolic trough, solar bowl or flat solar panels heat is captured from the sun. The cost per captured Watt varies but in bulk it hovers around 0.1 Euro per installed Watt. If this is done in places where the installation is most conveniently integrated into the lay of the houses the option of permanent self sustaining neighborhood solar emerges. For example unused flat roofs can harbor parabolic trough collectors for several houses, colletiors can be mounted on south facing side walls with lots of sun exposure. A church tower may be an ideal place to collect heat for the church and the people in the houses around it.
One can store thermal energy (heat) as such or as cold (which is more efficient). Central storage of heat is not uncommon, and many cities have city central heating (like New York. These installations are common technology (with possible improvements, true). This means one might want to use a basement, or use ground storage.
Upgrading heat and Solar Air Conditioning
Heat pump technology for use with 'waste' heat has yet to become realistically priced. It is now priced in accordance with the perception it is a new technology, but this is complete nonsense, your refrigerator is a heat pump and there are probably billions of those on Earth. The COP that is touted as an important factor in these systems loses that importance if one considers the solar energy is free. What is needed is an accurate assesment of what the cost of the installation is and what the yield in terms of delivered heat is, but keeping in mind going forward the only cost will be maintenance.
Compressed air is a less complicatec alternative for steam and can be turned into work and electricity using existing engines and microturbines. It might be transported trough the gas tubes already in place. It can be generated using solar steam and stored in simpel pressure tanks.
There are now reasonably priced steam generators. These can be used with vacuum tube collectors (that easily go over 150 degrees Celsius. Some electricity is needed for powering appliances and driving the heat pumps (although steam driven heat pumps would eventually become available). Photovoltaic panels would also be interesting as their capacity would likely be used up completely at all times. For electircal storage one could look at sharing with other neighborhoods, feeding back to the grid or using hydrogen fuel cells or flow batteries.
New York has the Infrastructure
Getting it Done
If you want to develop and organize this concept join the forum and send us a message at email@example.com . Also help us develop www.parabolictrough.org so together things become easier and cheaper for all.