I. Kites that pull out kite cables to turn ground-based electric turbines

I1. Kite electricity in light winds

Wind turbines are now cost-efficient in windy regions. Unfortunately, much of the earth doesn't have a nearby windy region. One solution is to reach higher into the air for steadier and stronger wind power. Wind turbine towers can't quite reach that high. Kites can reach almost any altitude.

I2. Predecessor: putting propellers and turbines on kites

Makani Power and others have designed airplane-shaped kites with propeller-like wind turbines on their wings. The first problem with this design is launching the wind blades and electric turbines into the air in light winds. Second, in use the extra turbine weight and drag in the airstream requires the use of a heavier cable. Finally, if the kite ever crashes the airborne turbines will be destroyed, and that type of frequent loss would be expensive.

I3. Kites that pull out kite cables to turn ground-based electric turbines

My electricity-generating kite is a kite that alternatively pulls its kite string or cable outward, where the pulling motion turns a wheel that spins an electric turbine. Then the kite stops its pulling, retracts back to its original position, and this process repeats. The process vaguely resembles the use of tidal kites to generate electricity.

My kite is a ribbed sail that can turn crossways against the prevailing wind stream for maximum cable pull horsepower and can then turn lengthwise against the wind for low-energy retraction to its start. Two such kites operating in tandem can turn a single electric turbine to generate continuous electricity all day. The system can work offshore, well-anchored to the sea bottom in deep water, on a floating base of operations. It also works in almost any light-wind onshore environment.

The maximum amount of power delivered to the electric turbine is limited by the breaking strength of the kite's cable, multiplied by the wind speed aloft minus a slight inefficiency penalty for wind spill and for the kite's retraction phase. For example, a kite/parasail might be sized to pull the cable out at perhaps .3 meters per second below the upper air wind speed. If the air pushes the kite at a mere 1 meter per second (5.79 mph) and the test strength of the cable is 1000 kilograms (2200 pounds), then the reel is pulled around at 1000 newton-meters per second, or 1.3 horsepower. If the wind speed is 10 meters per second (33 m/sec), (20 mph), the reel is turned with 13 horsepower. Notice that the usable horsepower is rarely zero unless winds are almost completely calm. The kite generates at least some power most of the time that normal wind turbines are offline.

I4. Balloon/kite combinations can reach well into the atmosphere

Decades ago I tried attaching a string of helium-filled balloons to kite string in order to position a balloon-lifted protest message in the air half a mile downwind. The experiment half-worked, except unfortunately half of the helium balloons had popped in the open back of a pickup truck before we reached the demonstration site.

The weight of an extremely long and strong kite cable can be countered by attaching hydrogen-filled teardrop-shaped balloons to sections of the kite cable.

As an inventor I don't believe in building large-scale green hydrogen pipeline networks. The fuel is inherently harder to handle than other fuels. However, green hydrogen (hydrogen not made from natural gas) has one uncommon advantage – it can be manufactured onsite from salty water and from solar electricity. Salty water and photovoltaic power are available almost anywhere.

Lighter-than-air hydrogen contained within an unmanned balloon is rather safe. If hydrogen starts to leak out of a small balloon hole, there's nothing in the sky to start the hydrogen gas burning before the gas dissipates in the atmosphere. The hydrogen gas molecules soon become water molecules.

Lighter than air balloon support means that a relatively economical, durable, non-ultralight cable can be used as a kite string. I expect that a string of aerodynamic balloons and a lighter-than-air kite can lift a relatively heavy cable well into the atmosphere in order to harness stronger winds at higher altitudes. With enough intermediate balloons the kite can catch the prevailing wind at any altitude.

We might want to reach 300 meters of altitude, where 300 meters is understood in the USA as the lower aviation limit for commercial planes not near an airport. To reach that altitude we might want to deploy a minimum of 1200 meters of cable plus have another 300 meters of linked chain deployed on the reel.

Balloons can make launching and retrieving the kite easier in tricky ground-level winds. Too many children's kites have landed on sharp objects on the ground upon launch or have gotten caught in trees. A series of balloons able to lift more than the cable's weight would be less likely to get pulled to the ground in a downdraft.

The kite should have ribs filled with a lighter-than-air gas. The name “kytoon” was applied to kite-balloon combinations in World War II. I'm not a fan of parachute-like kites for this job because a sudden wind gust can twist such a kite into a figure-8 shape, with no easy way to rectify the twist in the air.

I5. A linked chain for each kite’s reel

See also: G2. Linked chains with smooth, precipitation-resistant tops

A linked chain of perhaps 300 meters is attached at the ground end to a large reel that rolls the chain into a spiral of gears on the reel, keeping the cable from ever fouling at the reel end. 30 spiral turns on a 3 meter diameter wheel will hold roughly 300 meters of linked chain. As described earlier, the top of my own linked chain would be built with a roof that keeps any flying branches out of the chain gears. The chain is wound on the top of its reel to put the gear holes on the bottom of the reel. The reel moves with the wind direction to keep the chain pointed straight toward the kite.

This particular linked chain can have good distances between adjacent links on the chain. It’s possible for the chain to have individual links that are up to 1 meter long, provided of course that the gear teeth on a ten meter diameter reel are constructed to match these links.

At the top end of the first chain is the first support balloon. This balloon helps to keep the chain out of the dirt in bad wind gusts. Beyond the first balloon a flexible lightweight cable is better than a linked chain, as the cable won't be alternatively bent around the reel and then straightened all day and night. More balloons support more sections of the cable as needed.

Linkages for attaching the balloons are clamped onto the cable. In times of no breeze the balloons can be detached, deflated and stored, and the cable can be wound on the reel.

The top end of the cable is a balloon/kite. The hydrogen-filled balloon kite is positively buoyant in the air to help support the cable and to reduce the effects of strong downdrafts. The kite needs to be able to correct its attitude after a rare crazy wind gust flips it.

It's able to pull on its own cables to flip itself into pull-out position, pretty much catching the wind like a parachute while maintaining altitude, and into retract position, pretty much minimizing its drag while maintaining altitude. Different pull-out positions apply different amounts of stress to the cable. The system needs to calibrate its pull on the cable to deliver maximum cable pull on the reel, but without exceeding the cable's rated strength.

If the cable ever breaks, the kite optimally can release its buoyant gas and then steer itself down to a relatively safe landing spot or a tower that safely snags the remaining kite string.

Install two balloon kite on two connected reels. One kite has a longer kite cable and operates underneath the other kite. When the second balloon kite pulls out, the first balloon kite retracts, and vice-versa. A gear system allows for each balloon to pull on the system's electric turbine in 55% of a cycle and then retract in 45% of the cycle, with a short time for a smooth crossover between the two kites, allowing for an effective 100% power generation time all day and all night.

Given light wind speeds, 80% renewables coverage might be possible.

The two kites should pull on the reel in the same direction. One kite should have a longer cable and should be farther downwind than the other kite. The kite with the longer cable should deploy from the bottom of the big cylinder reel, and the kite with the shorter cable heading up at a steeper angle should deploy from the top of the big cylinder reel. The big cylinder reel with its electric turbine rotates with prevailing wind direction.

In s 3 mph wind, a kite that pulls upward at a 45 degree angle would deliver its maximum pull at about 4.4 miles per hour. Pull speed times the cable's maximum load equals power. This leaves open the possibility that the kites could tack either vertically or horizontally to gain more pull speed than the existing wind speed, increasing power on almost calm days to the system's maximum power load. A bigger kite would help on that day. at a time.

On a day forecasted for higher winds a smaller, more suitable kite can be deployed or we can reef the sails on the balloon kite. On extremely windy days, stow the balloons in their hangers and let the regular wind turbines handle the load.

Put blinking warning lights on everything and don’t operate above 300 meters so as not to be an aviation hazard. It may be possible to send an AC current up the cable on auxiliary wires. Batteries and tiny wind turbines might also work. Illuminating the balloons from the ground with flashes might work. Spotting small planes on radar and directing warning sounds right at them with megaphones or with sound cannons might work.

Duplicate: Motorcycle chains and gears on the ground

The bottom section of the kite cable, from the maximum extension of the kite at the end of the pull phase to the minimum extension at the end of the retrieval phase, is a type of roller chain. Roller chains can interface with gear teeth on a roller, translating pull to a circular motion. Most electric turbines use the motion of a wheel to generate power.

The roller chain wheel can wind up and release the roller chain in a spiral. We could wind 1000 meters of chain on a 10 meter circumference reel if needed. The roller chain wheel would rotate depending on the direction of the

With a large enough diameter roller chain wheel, we won't need as many roller chain links and so we can economize on the linked chain with longer gaps between links.

The reel probably should be mounted at some height above the ground or on top of a hill, because in a soft or zero wind one of the chains might dip below the reel's elevation when the chain is fully deployed. This is another argument for intermediate cable balloons or intermediate cable kites.

I6. Kite design and control

I assume neoprene kite ribs for now. With a large kite, compression, pulling together, is accomplished with a cable and pushing parts of the kites apart is accomplished with air pressure, with roundish hydrogen-filled ribs inside the kite. At times two sets of ribs are used, where the outer set of inflatable ribs keeps a certain airfoil shape to the kite and the inner, higher-pressure ribs keep the kite's shape in unexpected wind gusts.

Given a bad wind gust a flimsy kite can, like a spinnaker, get caught in a dreaded figure 8 deployment. No one is up there to fix the sail. Therefore I recommend inflation ribs on the kite, filled with hydrogen for cable support and for easier kite handling near the ground. The kite needs to shift abruptly from retrieval phase into pull phase and then quickly back into retrieval phase all day. That's why a stiff kite should help.

The reader should notice that this kite looks like a sail, not like a pulling parachute. In extremely light winds a sail can tack with the wind, pulling on the kite's tow cable with greater speed. Not shown, and still to be added, are attitude control fins so that the kite sail doesn't spin upside down in perverse winds.

The whole kite is streamlined. Overall I see an airplane wing with a slightly bulging front end to the wing, tapering to a thin tail for lift. The kite will always be approaching the wind at a specific angle during the retrieval phase. Often the kite blocks air like a spinnaker during the pull phase. It's possible to have spinnaker attachments on both sides of the two main ribs, or on the tail with a tail rope to pull on the spinnaker, except the kite needs to start pulling on the cable quickly and with 99.999% effectiveness.

I'm going to recommend two round, long, fairly large and stiff air ribs on the kite's left and right sides. Between the two outer tubes would be a long set of touching parallel inflated ribs. The touching ribs are connected by fabric on their sides. All parallel ribs would emulate an airplane's wing, just a bit rounded on the front ends, tapering to zero on the tail ends. By connecting the sides of adjacent tubes, sideways stiffness is enforced across the kite.

The effect is like an air mattress, with a long series of bumps from left to right across the kite. Parallel rib bulges are on the top of the kite and on the bottom of the kite. From front to back, the airflow line is always smooth.

The front ends of the two long outer tubes have the two ends of sort of a suspension bridge, bowing inward between the ends, across the kite's surface. The two long outer tubes keep the curved front end stiff into the wind. The same suspension bridge philosophy keeps the tail end of the kite stiff.

I7. Kite control

The two outer tubes each have two flaps of fabric leading downward to grommets. Four guy wires come down to a wire pulling system where the main cable connects.

Pulling in the two forward cables makes the kite cut into the wind, lowering wind resistance for the retrieval phase. Releasing the wire on these two forward cables turns the kite up into the wind, creating strong wind resistance for the pull phase.

Warping the kite balloon by pulling in diagonally opposing cables turns the balloon's orientation from straight up to left or right in the sky. The balloon is able to tack left or right.

At night, lasers can shine blinking lights on the balloons and the kite to warn aircraft. On a rare occasion the kite's software will need to direct the kite to evade a wayward airplane.

I8. Support balloons

A tether with periodic support balloons can reach to any height for steady wind.

I see the kite cable as containing attachments where balloons can be securely locked onto the cable. The attachments are streamlined so that the cable can still be reeled in as needed, and the balloons can be independently stowed and maintained in balloon houses. Having a spare balloon onsite would be good for system reliability.

For each kite, have perhaps two long, streamlined, teardrop-shaped hydrogen balloons holding up the intermediate pieces of the cable. Each balloon has a tethering cable that locks onto the main cable.

Alternatively, each support balloon can be an extra kite surface. All of the kite surfaces can simultaneously pull and be retrieved on the same cable, delivering even more power down a double-strength cable to the ground station.