About 10¹⁷ watts of incident solar power continuously reaches the earth's surface.  More than 10% of it can be harvested globally, at competitive prices, by carefree, attractive, safe, building-integral photovoltaic (PV) solar panels and wind turbine installations, combined with power storage/regeneration.  It's enough to supply all future electric power needs.

No land needs to be allocated for harvesting this power, because the PV can also serve as roofing, exterior walls, and windows, for the buildings they power.  Even the wind turbines can be part of the buildings, which can increase wind-speed at the turbines by funneling it.  That has been demonstrated in wind-tunnel tests.  To meet this challenge, tomorrow's great architects will probably work with electrical engineers and aerodynamicists.

Sun and wind are statistically predictable and dependable, but power that can be harvested from them will not coincide with electric power demand.  With safe, reliable, and efficient on-site power storage/regeneration, building-integral solar and wind power yields can be maximized and available on demand.  None of these technologies would pollute our air, water, or land, or cause global warming.

Most of us have seen or know about the vast arrays of mirrors which concentrate sun on a boiler to drive steam turbines, and the miles of tall towers with wind turbines that generate 60-Hz power in windy locations. They are connected to utility power grid transmission lines, and generate electric power which supplements the grid's central generating plants, powered mainly by fuel-burning, hydro, nuclear, etc.  Also, large scale photovoltaics have been proposed, whose DC outputs would be converted to 60-Hz, synchronized to connecting grid transmission lines. They need large areas for such installations. Most "wind farm" generators are induction machines, which generate power only over a narrow speed range. Power plant transmission lines connected to them are subjected to disruptions from these generators that have caused grid failure. So power utilities limit the number of such generators.

But few of us have seen building-integral photovoltaic (PV) solar panels.  Some who have seen them on buildings,  may have thought they were conventional roof-tile, wall sheathing, or tinted glass.  Photos of existing building-integral PV installations are shown below.

Left: Residential building with solar tile roof.  Center: Rest-stop shade/shelter with solar panel roof.  Right: Office building with solar panel roof, walls, and windows.

Fewer, or none of us, have seen on-site building-integral wind power installations, despite their evident practicality:  They can use the buildings they serve, as substitutes for towers; and these buildings can also provide wind-funneling to turbine blades, weather protection for the turbines, and screens to protect people and birds from the moving blades.  Moreover, wind power is usually higher during storms, when solar power is less, so they are good complementary "green power" sources, that minimize total power storage needs.

See illustrations/links below, of solar and wind powered buildings, an electric highway that supplies in-transit EV power, and an EV with onboard PV/battery/pedal power.

Clean sustainable solar and wind power, like that illustrated above, would afford  profound global economic and environmental benefits for all.  As explained below (if you have a little patience to follow the simple math presented, or, better yet, if you choose to do your own math), it is cost-effective by any measure, and does not cause air, water, and site pollution, global warming, or dependence on tenable fuel supplies that pollute.

However, to provide uninterruptible power during grid outages, or enable future off-grid on-site solar and wind power installations, viable on-site power storage and regeneration systems are needed, that are not yet available.  Lead-acid batteries, with their poor reliability, high maintenance expense, hot and cold temperature limits, and toxic waste problems, are still the most practical and widely used power storage option.  But new options from RPM, without these drawbacks, can be available in 2 years.

RPM (Regenerative Power & Motion) is developing on-site power storage and regeneration systems, that will greatly enhance building-integral solar and wind power.  See illustration/link:  These systems have practically zero idling losses (i.e., low self-discharge), ultra-efficient power transfers (~95%) and ultra-high reliability.  They will not need maintenance over their entire (20-year warranty) life.  Their energy storage components can be installed in a safe site, because they won't need servicing like others, while their electronics can be readily accessible for setting control options and status monitoring.  These systems will provide dependable on-site UPS (Uninterruptible Power Supply) having far higher reliability and lower annual cost, than all existing on-site UPS options.

For low-earth-orbit and geo-stationary communications satellites, RPM's UPS can provide pitch, roll, and yaw control, besides ultra-reliable power on demand, replenished by onboard PV during sunlit hours (12 hours charging and 12 hours supplying power, daily, for geo-stationary satellites).  RPM's system requires no precession torque actuators; its radial servos with their radial electromagnets can do that.  And it eliminates need for jet thrustors now used for pitch, yaw, and roll maneuvers.  Also, its ultra-low power losses minimize total weight and size, for both the UPS and the PV panels.

Wide ambient temperature range tolerance, ultra-high reliability, and minimum overall (including PV) size and weight, make RPM's UPS ideal for any possible solar powered planet stations, that may be contemplated.  Ultra-low idling loss is crucial to providing regenerated power during the moon's ~ 360-hour nights.  Yes, we could one day have a permanent solar/UPS powered installation to go to, on the moon or Mars.

Future RPM UPS earth applications (by far the most important business application for RPM flywheel battery technology) include carefree solar/wind-powered buildings, and even electric highways, that can supply in-transit power to high-performance dual-mode EVs.

We can establish realistic costs and power losses, from a few viewpoints and formats, for both centralized solar power "farms" that feed a 60-Hz grid, and on-site building-integral photovoltaic panels that feed a local DC bus.  The two different formats selected below seem to be the most appropriate and informative for the situations they analyze.

Most electric appliances now use 60-Hz.  But most will operate well from DC power, or could be designed to work directly from a DC bus, and so have higher efficiency, and even cost less than conventional electronic appliances (because they won't need AC input power rectifiers and hold-up capacitors):

On-site building-integral photovoltaic panels + boost converter + wind-powered generator + flywheel UPS

PV panel cost ~$4 per watt generated ~8 hours per day.
PV panel area ~0.16 sq.ft. per watt. A typical residential installation might have ~500 sq.ft. of PV, costing $12000, that gives ~3-KW of DC power ~8 hours/day.   It can be used instead of roofing, exterior wall cover, awnings, and tinted windows.  So overall cost is less, by these replaced materials.

Building-integral wind turbines don't need towers. RPM tested and proven broad-speed-range DC generators produce energy yields more than 2x any other available generators, with far better power quality. Their power ratings are easily matched to turbines that will drive them. Their on-site installation can channel wind to them so wind speed is at least doubled at their turbines (so power is at least 8x), and can be limited by passive vane control. The vanes also protect birds from their turbine blades. Such turbines and generators, costing about $4000, can generate on average about 10-KWH/day.  

Boost converter (dc bus voltage regulator and power yield maximizer) costs ~$0.3 per watt, has power losses of ~4%.
Power storage/regeneration will have losses ~12%.

On-site power storage/regeneration and UPS cost may be ~$12000 for a 20-KWH storage/regeneration 4-KW maximum power system.

Over a 20-year service life, $28000 invested at time of installation would provide an electric energy yield (kilo-watt-hours) =
(24KWH+10KWH)/day x (360day/year) x (20year) = 244000-KWH
So uninterruptible power cost per KWH energy is ($28000)/(244000KWH) ~ $0.11 per KWH.

Combining on-site solar and wind power would facilitate shared UPS power storage/regeneration.  This would reduce overall cost for on-site power storage/regeneration, since wind and solar power usually peaks at different times.

This clean, non-polluting on-site power costs less than present utility power prices.  And it includes on-site UPS.  Although the power industry does not price their services to include a fee representing power quality and reliability, its value can be established.  EPRI (Electric Power Research Institute), a US organization financed by the electric power industry, estimates a fast rising ~ $100 billion yearly US business financial loss, due to power outages, sags, and spikes.

Also, prices for PV and wind turbine generators, and for planned on-site power storage/regeneration UPS, will surely decline as products mature and manufacturing is scaled up.

On-site solar/wind prices, for remote site  installations, are considerably lower than utility power, which include grid transmission line costs of typically over $10,000 per mile from existing power lines.

Those who may argue that there is not enough available land, to capture enough solar power to make a difference, have obviously not considered building-integral solar/wind and UPS.  The 500 sq.ft. of PV in the above example surely does not need land rights, for solar panels, wind turbines, and UPS, which makes enough power available on demand, to supply all power needs for a typical residence.  Systems for commercial or office structures would be accordingly scaled.

Centralized grid solar panels + mounting structure + 60-Hz inverter + step-up transformer + high-voltage transmission lines + step-down transformer

PV panel cost $4 per watt generated ~8 hours per day.
PV panel area ~0.16 sq.ft. per watt.  It needs a support structure, costing ~$0.4 per watt.  Cost of vast real estate use is not estimated or included here, but may be considerable.

60-Hz inverter cost ~$0.3 per watt, has power losses of ~5%.

Step-up transformer costs $0.2 per watt, has power losses of ~5%.

High-voltage transmission line and land rights costs are not estimated or included here, but may be considerable.  Power loss ~10%.

Step-down transformer costs $0.2 per watt, has power losses of ~5%.

So overall PV power cost = ($4+$0.4+$0.3+$0.2+$0.2) = $5.1/watt capacity.

Again using a 20-year service life, that most manufacturers offer for PV, $5.1 invested at time of installation would provide an electric energy yield (kilo-watt-hours) =
(1watt) x (1KW/1000watt) x (8H/day) x (360day/year) x (20year) = 57-KWH
So cost per KWH is ($5.1)/(57KWH) = $0.09 per KWH.

Utilities generally add power transmission cost, amounting to about $0.09 per KWH, so customer charge is about $0.18 per KWH.

We can also establish present power costs, for on-site building-integral wind turbines that feed a local dc bus, and wind power "farms" that feed 60-Hz grids.  Electric power from wind turbines is sporadic, and not dependably predicted at any given time.  However, long-term yield from known average wind speed can be predicted by statistical computation, based on a Rayleigh distribution of probable hours at a given speed, as described in my webpage on solar/wind power.  Results of sample approximate computations are presented below:

Wind turbine with generator synchronized to 60-Hz grid

Cost of 20-ft. diameter axial wind turbine and mount ~$10,000

Cost of generator mounted on turbine shaft $2000

Cost of tower ~$5,000
Cost of land use, which may be considerable, is not included here.

Estimated electric energy yield over 20-year service life ~100,000-KWH
for 300-sq.ft. turbine, connected only at wind speeds between 30-mph to 40-mph,
in 20-mile/hr. average wind speed at overall 40% power conversion efficiency.

Step-up transformer costs $500 and has power losses of ~5%.

High-voltage transmission line and land rights costs are not estimated or included here, but may be considerable.  Transmission power loss ~10%.

Step-down transformer costs $500 and has power losses of ~5%.

So estimated cost/KWH = ($10000+$2000+$5000+$1000)/(100,000KWH) ~ $0.18/KWH.

The above simple calculations don't include interest.  Nor do they attempt to estimate rising future cost of conventional power. Conversely, possible government subsidies may reduce the cost estimates presented here.  Or if compared to conventional electric power price, which is about $0.15 per KWH for most households, they do not consider the present and future indirect costs of environmental pollution from mining and burning fossil fuels, or dealing with nuclear waste.  Those costs will probably soon be included in billing to grid power customers.

For more about RPM's technology, how it can improve power quality, and how it can enable practical lower-cost on-site solar and wind power -- and much more -- visit these links: