Water Pile

1. Introduction

Water Pile is a citizen driven low cost distributed gravity energy storage using dense water.

Water Pile distributes the responsibilities and benefits of running gravity energy storage to many sites, overcoming the long lead time, large capital and operating expenses that other gravity energy storages experience.

Excess power is used to pump water from a number of Bottom Tanks to a number of Top Tanks, while water from the Top Tanks are used to drive turbine when stored power is required. The specific tanks involved each time can be different, depending on how much flow is required, how high they are, how much water is left in them etc.

2. Unique Features

Water Pile is unique in many ways, unlike existing gravity energy storage which is built and owned by a single entity, Water Pile's construction, operation and ownership are distribute amongst many entities.

waterpile

Water Pile has multiple computer controlled water tanks working together with each other along with a grid of computer controlled turbines to maximise power output and minimise cost.

  1. Multiple Tank Heights
    On most sites it is not possible to install a large water tank at the highest altitude. Water Pile installs whatever volume tank is possible and then install more tanks at lower attitudes, taking maximum advantage of all possible spaces for storage of water at elevated heights.

  2. Variable Tank Shapes
    On most sites it is not possible to install a large circular tanks. Since each Water Pile tank does not hold a massive volume of water, Water Pile can use water tanks of any shape and size e.g. wrapping themselves around the wind turbine tower on the outside or filling up the spaces around the ladder inside the wind turbine tower.

  3. Multiple Tank Aggregation
    The feed of all tanks to the turbine is controlled individually so the maximum head and flow is achieved. Multiple tanks can feed the turbine together to when extra power is needed. The highest tank can be filled first and lowest tank can be emptied first while excess power is available.

  4. Dense Water
    To increase the mass being moved around and thus increase the energy available, additives (e.g. salt, sugar etc.) can be added to the water. Some ingredients can be dissolved much more than others (e.g. fucose vs glucose) and chemical (e.g. trehalose) can be added to super-saturated sugar water to prevent crystallisation.
    Since the potential energy at height is directly proportional to the mass, an 50% increase in density of the water will result in a 50% increase in energy. Water Pile's optional close loop design makes the use of high density water (and thus the increase in energy) possible.

  5. Multiple Ownerships
    Tanks does not have to belong to the one owner non even on the same site. Due to the low density of water, aggregation is required to increase total power output. Allowing different ownership means tanks over a large geographical area can be aggregated.

  6. Modular Tank Capacity
    Water Pile is the cheapest to deploy gravity energy storage, however to reduce capital expenditure even more, extra tanks can be added progressively as required to take up excess electricity. The system will adjust itself to maintain the highest head and flow by taking into account of the newly added tanks.

  7. Encourage Local Use
    Low cost, low footprint and use of existing structures means Water Pile can be deployed not just in sites with electricity generation (solar panels) and electricity distribution (transmission towers) but also at the electricity consumption points (say there are different peak and non-peak rates for electricity).
    Having low cost electricity storage available nearby is advantageous to every part of the electricity infrastructure.

  8. Community Power Aggregation
    Besides aggregating their tanks (to increase flow and capacity) to feed the turbines, communities can also aggregate at the power output level. Water turbine electricity output are synchronised so they can act together as a single grid to supply electricity to other points on the grid.

  9. Turbine Communication Mesh
    A independent communication mesh (e.g. WiFi and LoRA) that is NOT connected to the internet allows all turbines and tanks on the same grid to communicate with each other in order to maximise output and minimise cost.
    Nodes (turbines and tanks) can communicate with far away nodes through intermediate nodes in the middle. Data are routed through other nodes when a node in the middle fails.

Will a million water tanks working together deliver the same benefits as a million mobile phones?

3. Wind Turbines

Wind energy is much more variable than solar energy, storing excess energy at the source with each wind turbine individually could revolutionise the whole industry.

Since the energy is stored at the wind turbine itself, there is no need for a separate storage site and no transmission lost.

windenergy

Wind turbines are very tall structures with limited volume for tanks, by breaking that height up into many tanks, it is possible to maintain a high "head" value by always filling and using the higher Top Tanks first (the lower Top Tanks will only be used when the higher Top Tanks are empty).

This is particularly suited to sites with high frequency of wind speed variations, as the highest Top Tanks will be filled and emptied continuously.

In cases where higher flow (higher power) is required, multiple Tops Tanks can be combined together to drive a single water turbine. If even higher flow is required, tanks from multiple wind turbines can be combined together.

For wind farms with more than one wind turbine, it can more economical to aggregate the flow and have one water turbine serving a number of wind turbines.

4. Tall Structures

A lot of human made structures like buildings and high voltage transmission towers are tall enough and close enough to each other make Water Pile deployment viable.

structures

Although it is possible to build standalone Water Pile towers to store energy, it is much better to have Water Pile deployed near energy sources to leverage their physical structure and the reduce any of power transmission lost.

Buildings might have solar array on the roof and a lot of large internal voids (e.g. fire stairwells) where Water Pile tanks can be mounted on different floors to reduce demand for precious lithium (which light weight is not really needed in a building).

Electricity towers already have electricity running overhead and are normally of much stronger built than telecommunication towers. Having Water Piles located at the transmission towers can smooth out the supply and demand curve of the whole electricity infrastructure (whether it is from renewable or not).

5. Natural Features

Most countries have cliffs either along the coastline or in the mountains near power sources or transmission towers. Water Pile's flexible tank shape means it can be deployed quickly and non-intrusively to provide storage near those sources.

The vertical drop of the cliffs is not required in a lot of cases e.g. the Water Pile tanks can be arrange on a slope.

slope

As long as there are structure to support the water tanks, whether is it a deep hole or a tall cliff, a hilly suburb or an open cut mine does not matter. The idea is simply to dynamically adjust usage of multiple tanks at different height so the head and flow can remain the highest possible at all times.

Like all Water Pile deployments, the more numbers deployed nearby the better, to compensate for water's low density. Normally multiple Water Piles will be deployed together along the cliffs or on the slopes.

6. Community Aggregation

A lot of cities around the world are hilly, with many houses built on the slopes at different highs. Water Pile can combine the tanks in all those houses into a giant battery.

community_battery

Houses on the middle of the hill can have either top or bottom tanks depending on demand, the idea is try NOT to use them, if tanks above or below them are available, to maximise "head".

Depending on the diversity required, each house can feed one or more turbine at the bottom of the hill. All tanks are part of the Turbine Communication Mesh, so all components within the mesh, tanks and turbines, can work together seamless to maximise head and flow.

7. Initial Deployment

Initially we are looking at hilly suburbs with a lot of solar panels installed. So two neighbours with large elevation differences between their properties can start working together to seed a future community battery, making it easy for other neighbours to join in.

  • May be we start with two Hollywood stars with houses on Beverly Hills ?
    A marriage of art and science ?
  • What about the 504 metres high lift shaft in Burj Khalifa ?
    There must be some space along the walls ?

8. Why Water ?

There are hundreds of ways to store energy, from moving dirt up hill to compressing air to exotic chemical processes to keeping something really hot ... all very complex, fragile and expensive - compared to water.

  • plumbers are easier to find than engineers
  • anyone can spot a good location to place a tank without special equipment
  • many can repair a leak or turn a tap off
  • if there is an accident people get wet - with those other technologies ... emm ...

We need very large scale, we need small footprint, we need ultra low capital and operation costs. Yes, water tank as a gravity store has a poor energy density but when there are a million of them working together intelligently ...

As the only blue planet in the our solar system, why not make more use of something so abundant yet precious ?

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