One needs to consider the penultimate source of the energy one wishes to utilize. (The sun is the ultimate source and the only other source of energy on earth is radioactivity which was "manufactured" by previous suns/stars.) Some organisms use this source of energy at "vents" in the sea and hydro-thermal springs. All life uses energy originally sourced from the suns (note the plural suns.)
The main energy in a thunderstorm is gaseous water which makes heat as it condenses into rain (excuse the loose terminology). This sustains a thunderstorm although it is started by having a gradient of temperatures vs altitude build up such that any parcel of "warm" air that begins to rise and consequently expand (which cools the parcel) finds itself in surrounding air that is cooler than itself, thus it will continue to rise.
Counter-intuitively one requires the atmosphere to get cooler "quickly" with altitude to enable this process
It eventually cools off enough so that water vapor that it contains condenses thus providing enough energy to prevent the remaining gases of the air from getting cooler (and thus sinking)
In a manner of speaking thunderstorms "suck" from the top. Gliders avoid thunderstorms (or at least gaining an altitude within them where the uplift is so fast that the turbulence rips the aircraft apart) One glider reached an altitude of 53,000 feet delivering its dead pilot "safely" to ground. Even if one has 100% oxygen to breathe, once one is above 36,000 feet where the pressure is 1/4 of that at sea level, no one survives without "pressurization" due to the respiration rate required. People have climbed Everest (approx 30,000 feet) without supplemental oxygen.
As one gains height one gains stored potential energy but only in a "heavier than air machine" which a blimp is not.
The power of lightning can be great but its lifetime is very short thus the total energy is minimal. The utilizable (total) electrical energy in a thunderstorm can be estimated by the number of lightning strikes it produces and even this is not relatively significant.
We do use hydro-electrical energy some of which comes from thunderstorms as opposed to plain rain.
I hope this illuminates the problems posed by the question.