Session: 09-05-01: Hydrogen and Energy Storage

Paper Number: 106209

106209 - Energy Storage and Direct Air Carbon Capture for Deep Water Energy Sources 

Power intermittency associated with many forms of renewable energy has been a significant challenge to overcome since their increased contributions to our grids. Innovations in energy storage technology continue to come about in order to address the need for more steady and reliable power from intermittent sources. In addition to this problem, there exists the global climate crisis driven by increased greenhouses gases in the atmosphere.  In light of this, there is a movement to implement infrastructure which captures carbon dioxide directly from the atmosphere (DACS) which is often encouraged by tax incentives. Our design for an offshore energy storage system seeks to provide solutions to both challenges into a consolidated system.

Offshore sources of energy such as wind power are becoming increasingly popular in coastal countries as winds are often stronger out at sea. With the emergence of floating turbines, the trend has been to build these turbines farther from coast and in deeper waters. These depths can be taken advantage of in a multitude of ways. The first of these is the storage of energy via buoyancy forces. Conceptually similar to a pumped hydro system, work can be done during excess power production to bring buoyant bodies to the ocean floor, and energy can be recovered by releasing these bodies up to the surface as required.

If these buoyant bodies were composed of air, this process could additionally involve the separation and storage of carbon dioxide from said air. At approximately 400m in depth, the hydrostatic pressure is enough to condense carbon dioxide while keeping the other components of air gaseous. This can allow for carbon dioxide to easily separate from the air via gravity.

This paper presents a combination of these two concepts into a single system, wherein a motorized cable system is built around an energy source such as a floating offshore turbine. Attached to this cable system is series of “gondola” containers which are filled with air and submerged to 400m below the surface. At this depth, carbon dioxide is liquified and separated from the air into a separate container via pressure-operated valves within the gondola. When energy recovery is desired, gondolas are released and upwards buoyancy forces turn a generator which sell back to the grid. Air from the gondolas is then exhausted, carbon dioxide is removed and stored, and new air is added to the gondolas for another cycle. Preliminary numbers (which do not yet include friction forces or power consumption from compressors) suggest an over 90% efficiency for this proposed system and approximately 5MWh of capacity. Additionally, carbon capture rates are currently estimated at approximately 15kg of recovery per full 13-minute cycle.

The paper provides a breakdown of this proposed system and its components, as well as an analysis on energy storage, power discharge rates, efficiency, capital/operational costs, product lifespan and return on investment. The rate of carbon capture is analyzed in relation to governmental incentives and added value to the product. These are all measured in comparison to competing energy storage products.

Presenting Author: Graydon Hands University of Calgary

Presenting Author Biography: I am a 4th-year student completing a Bachelor of Science in Energy Engineering at the University of Calgary. This submission reflects a part of a final-year capstone project which will be complete in April.

Previously, I graduated with a diploma in Power Engineering Technology at the Southern Alberta Institute of Technology wherein I developed technical knowledge and experience relating to power systems and I acquired governmental certification to operate said systems (ABSA 4th class operator).

Since then, I have attained working experience in coordinating projects in both hydrocarbon and renewable sectors. These include projects relating to pipeline crossings, salt-caverns and distillation facilities, as well as the construction of a 465MW solar farm (to which I dedicated 8 months).

I and my team have a strong passion for the energy industry, and the topics covered in our design submission tackle industry issues which we all hold as significant.

Authors:

Graydon Hands University of Calgary
Kevin Truong University of Calgary
Yvan Unico University of Calgary
Areeb Ashar University of Calgary
Ali Al-Saiedy University of Calgary
Roman Shor University of Calgary