First - a bit more on 'waste' heat. Remember that the primary thing we're working on here is to introduce waste products from earlier cycles as inputs into later cycles. We did this with the waste water from thermal separation being fed into the living machine -- which is a support structure to the vertical farm -- which then feeds fresh water back into the potable water supply that our residents use which feeds back into the thermal separation... etc.
Heat in our current environment is something to be shed. Like rain water off a building current standards say we want to move it away... not use it locally. HVAC systems (Air conditioning) is built on the concept of piping heat out of the interior space and radiating it into the atmosphere.
Think about what energy usage is in the modern home - and the common, usually unwanted side-effect of using electicial devices - Heat. We use things in our homes that generate heat. Things like computers, lights, pumps, water heaters, TV's DVD players and even cell phones. In fact - all those device that have wall worts (the black transformers that take up way too much room on the plug) generate a significant amount of heat as they convert the AC current into DC that the device itself uses.
So - modern energy usage involves the generation of large amounts of heat. Currently we try to let the atmosphere take it away... resulting in the phenomenon of Urban Heat Islands. We have to plan for this heat when we think about electricity and the power cycle. More later on that...
Lets look at the original set of power production possibilities:
* Solar, radiant and Panel based
* Geothermal
* Hydro
* Wind
Let's take this piece by piece - keeping in mind that *every* method for capturing and re-using energy will be used in varying degrees throughout the entire complex. Why use all of them? Because any one item can likely only be used at specific times or circumstances - making the power generation highly variable and not always available when we need it. We have to level that generation curve so that the power is not only available when we need it - it's being captured for later use when we don't. Additionally, extra power generation could be a profit center for the facility (someone owns this thing - thinking a MUD). Selling the extra power to the city grid could be an excellent method to subsidize lifestyles or other more expensive options to make the place attractive to the masses.
Solar
Photo-Voltaic panels on every 'sun-shade'
By placing solar panels on awnings, overhangs and other places where we humans want to stop sunlight (happens a lot during a Texas summer) we give ourselves a quick way to leverage roof space that by it's nature can't be a planted 'green roof'. Note that I'm not outlining that we put up these great big arrays way off to the side - rather I'm integrating them into the overall design: covering awnings, window shades, walkways and entrance ways.
Solar panels could be used along walls wherever the windows aren't. Right now, we cover areas like this with glass over concrete or just paint it white to shed the light & heat. Why not make that 'wasted' space a solar collection system and harvest it.
Additional positive bits on solar panels being sun-shields - it's distributed power generation that can be 'owned' by the location's owner. For instance - having a set of panels over my back patio means that the power generated by my panels is mine - powers my stuff first, and if there is extra - gets fed (sold) to the buildings power grid. For modern convenience and energy usage, it's unlikely that this single point of power generation will be anywhere close to enough. So - we move on to more centralized and industrial scale power generations.
Solar Thermal
Alternately - instead of photo-voltaic and direct power generation on the walls of our towers, we can do solar heat collection via mirror based power towers, parabolic channels or just simple black-box solar water heating. Hot water systems are a major use of energy in modern homes. Harvesting solar energy directly into hot water bypasses a large drain on our other electricity generation. If the heat is high enough to make steam - we get electricity generation via steam/turbine technologies. Again - we're likely to leverage more than just one method with the Gaia-Ship. Whatever makes sense given the location possibilities.
Solar gives us good peak generation during the day - a time when cooling needs are at their highest and human electrical use tends to spike because we're all awake & doing things.
Geothermal
Geothermal systems are great for steady electricity generation or energy storage. By tapping into either deep well heat or using the ground as a heat sink - we can generate some amount of electricity or regulate temperatures for heating & cooling throughout the facility respectively.
Unless the power plant is really big however and the wells deep enough to tap into mantle heat, direct power generation doesn't look like a good option for an Austin based Gaia Ship's electrical need. However - move us to California or areas of volcanism where the mantle is a good deal closer and Geothermal power generation begins to show real promise for high amounts of power.
So, we're going to focus on the thermal heat sink capabilities of a geothermal system.
Hydroelectric
Unless we find a great spot right on a steadily flowing stream - it's unlikely that we'll be using a more standard dam system for power generation. Also - only with really large amounts of steady flowing water does this provide enough power to provide for plenty of homes. Instead we can use hydroelectric as more a power storage system in conjunction with our water pressure system. At the tops of our towers we place large reservoirs that have water pumped up to them when energy is plentiful and allowed to drain over turbines down to basement reservoirs when we want to re-capture that gravity energy. Additionally, these turbines could be used to capture energy from rain-water capture as the water drains into our basement lakes.
So, Hydro and Geothermal may not cut it as major generation points but rather, supplemental and energy storage systems. Again - more on storage below.
Wind
Ah that greenest of energy generation. Lets explore a few options:
- Ridgeline
Most wind turbines are located on high natural ridges to get above the typical ground turbulence. Since we are in essence creating a man-made ridge we have the opportunity to line the top edge with that symbol of green energy generation. - Canyon effect
With buildings as large as the ones we're discussing - it's entirely likely that the breezeways built through the building could have generation possibilities. Have you ever walked past a building and had the wind go from a mild 2-5 miles per hour to what seems like a small hurricane? Buildings can be designed to channel typical and minor breezes into roaring walls of air. Most of the time, architects are attempting to minimize this effect - but what if we deliberately created wind tunnels and put big generators in them?
Even the normal breezeway could have small micro-generators (fans) above the normal walking areas. I envision these breezeway fans to be both energy micro-capture devices as well as powered fans that could help exhaust an area of undesired heat, unwanted smells or pollutants. - Man made Tornado
It's more comparable to a captured dust devil but by harnessing the cyclonic power of atmospheric heat rising we can create our own steady wind based generation. Cooling towers are the more typical method of moving waste heat away from a large facility, but by using a vortex you get to reclaim power from the heat that is being vented into the atmosphere.
Given the building design of a long winding ridgeline with towers rising above it in several places, we can place these artificial vortexes at the top of the towers to provide a facility wide heat exhaust system, a communal chimney for fireplaces, along with bathroom, kitchen and plumbing ventilation. The vortex creates a low pressure zone at the base of the cyclone which would draw air to it - heated or otherwise. This would be the sole method we would allow for heat to escape the clutches of our residential power plant.
Yup - there's more
More sources for electricity are needed you think? Yeah... me too! To many of the above sources are either not working all the time, or likely can't supply enough power to keep the lights on.
Our waste treatment plants provide the next major energy source. There's lots of stored energy in our trash and the thermal separation of that waste into Oil and Natural Gas provides a perfect source of stored power. If we don't need it and power is plentiful - say during a summer day, this oil is likely going to be used to make a form of diesel for vehicles. The natural gas will be burned in fireplaces and perhaps even in stoves for cooking (if it can be made pure enough) or separated into hydrogen for the hydrogen economy everyone keeps talking about. However, if we need it, putting it to use in boilers and heat generation is a very real option.
The nice thing about the thermal separation - it runs on only 19% of the natural gas it creates. That leaves 80% left for electricity generation for the rest of the Gaia Ship.
Our Bio machine - the artificial swamp - will be generating natural gases like methane that can be captured and put to use as well. Large agricultural facilities have already begun capping their animal sewage treatment ponds and using the vented methane to generate electricity to power their ranches or be transmitted to the nearby towns and homes. We'd do something similar here.
Stirling engines
Stirling engines work primarily on temperature differences. Neat thing about them is that they can work off really really low temperature differentials like your hand and the air above it. However - they work better with higher temperature differences.
Here is where we get to the heart of the power reclamation capabilities of a Gaia Ship. We've captured heat from many sources, channeled it into steam in some cases for turbines, hot water for others and now into a source for assorted Stirling engines.
By creating hot and cold zones we can use Stirling engines all over. Heat from solar thermal, burning oil and natural gas, wall warts, and human bodies all provide one side. Cooling from our water tanks, man-made glaciers (see energy storage below) and geothermal cooling provide the cold side of the mix. Any heat left over is vented through our artificial tornadoes.
Storing Energy
A recent conversation I had over easter dinner (Yay geek conversations at family functions) was on the different methods to store energy. One method I had read about was molten salt - but that requires some pretty hard-core infrastructure due to dealing with liquefied sodium a corrosive substance when it's NOT glowing like a lava flow. The method introduced to me at dinner was cold-storage in huge ice blocks. The idea is to use electricity to freeze water in huge volumes. Insulate it and it stays frozen for extended period with just the barest input of electricity due to the sheer volume of the ice. Kinda like why a glacier stays frozen all year long, even through hot summer days.
That ice could be used for cooling purposes (air conditioning) or as a thermal heat sink for Stirling engines. These man-made glaciers are really just large batteries that don't use any kind of toxic heavy metals.
Other more technical methods of storing energy include Supercapacitors and battery systems. Supercapacitors are going to be especially useful for our needs because we'll have such variable energy generation. Leveling it will be a big part of a large capacitor and transformer bank. Just setting up the supporting grid of electrical gear will be a major endeavor.
Given the expensive set up this is going to require, I really need to run some numbers to check and be sure that the combined power generation is at least 2x the peak needs of the 10,000 residents and guests. We gotta have some way to pay for this both immediately and long term.
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