The advantages of building a pilot ocean thermal energy conversion (OTEC) plant in Brazil

How could ocean thermal energy conversion support other offshore activities? OTEC is normally seen as concurrent of wind turbines when it comes to talk about offshore renewable energy. However, it is necessary to highlight the huge difference between those renewable energy concepts.  Those differences rely on the fact that OTEC systems can provide additional resources besides energy. We can affirm that Brazil should explore its vocation for ocean thermal conversion systems aiming to improve competitiveness of Brazilian oil and gas sector, contributing to the increment of its recovery factor, extending the life cycle of brown fields or even with the re-purpose of decommissioned floating units. Brazil should also increase fisheries production or simply produce electricity offshore and all those activities should be complemented, based on a synergy.

This is not a new concept. Norwegian companies and government have developed projects dedicated to integration between oil & gas units and offshore renewable electrification following the environmental characteristics of its coast, with strong winds and steep waves.  It seems that each country should follow its vocation. 

Brazil should explore offshore wind energy without losing touch with its vocation for thermal energy conversion, as well as many other countries located in the tropical zone with high solar irradiation. Besides its potential for integration with oil & gas industry, following the Norwegian model for wing energy, OTEC systems should provide desalinated water highly demanded by industry in the last years and provide nutrients for offshore mariculture activities, contributing to insert Brazil as one of the biggest fishing producers. In this summary we intend to detail the main aspects which motivate the interest from the stakeholders of the oil & gas markets, shipyards, industrial sector, and mariculture.

In order to make OTEC happen it is necessary to give the first step, with investments in a pilot plant which allows a deeper analysis of the system to provide precise information to scale up the plant for commercialization based on scientific method, useful to brazil and for all the remaining countries interested in this technology.

Brazilian Vocation to Renewable Energy

According to Offshore Energy Outlook, released by IEA in 2018, ocean energy tends to expand in next decades replacing energy produced from fossil fuel. This growth is expected in spite of competition with onshore alternatives. Offshore wind turbines for example, show a better capacity factor, however the distance from coast increases the complexity of operations as maintenance and installation, resulting in higher expenditures. The report indicates a trend of highly optimized projects, as well as the recent offshore oil and gas enterprises, based on the itegration with renewables, which are already a reality. 

In addition to a highly renewable energy matrix, Brazil is also a potential big player in the renewable ocean energy newborn sector. This is because Brazilian coast extends for 8.500 km adequate for any type of renewable energy. Oil and gas industry should be part of a more dynamic environment, in a context of synergy with other offshore activities.

Commercial renewable offshore energy plants are still expanding with offshore wind turbines in the northern countries and there is a great uncertainty about future oil and gas demand, as was remarked by IEA report (2018). It should be advantageous to Brazilian oil and gas companies or those foreign companies operating in Brazil to start taking a look at opportunities of integration between renewable and oil & gas industries. This will happen if a favorable environment is available in terms of regulation and project financing, besides university support.

 OTEC

Current investments on offshore renewable energy are concentrated on wind turbines while other techniques as wave, tidal and OTEC are still a bit forgotten. The prevalence of wind offshore is a result of decades of research carried out by northern countries, especially UK, Norway and Denmark with small scale and pilot plants. In Brazil ocean energy is still a concept, without any real perspective for wind offshore enterprises or any other ocean renewable option. It is a natural behavior to follow the countries that making it happen and wind offshore is an option for Brazil. Nevertheless, it is important to remark that probably OTEC was not as developed as wind energy by those northern countries because of its ocean temperature profile. Wind energy is a vocation for northern countries as well as OTEC is a vocation for countries located close to tropical zone.

OTEC was already tested in the 1920’s in Brazilian coast by French scientist George Claude. A floating facility was installed in front of Rio de Janeiro coast aiming to produce ice for summer time in Brazil. Unfortunately at that time George Claude didn’t succeed since a failure of the cold water pipe, used to bring cold water from deep sea to surface, anticipated the end of his experiment.

Ocean thermal energy conversion is characterized by drawbacks and advantages, as well as any other renewable source. Low efficiency is one of the main barriers and a lot of scientific research has been performed in order to overcome those obstacles as can be seen in the work published by Stefano Landini (2015). On the other hand, maybe the many advantages of OTEC make it look like a panacea, not a real thing. Besides producing energy 24/7 as base load OTEC provides byproducts as desalinated water, refrigeration, and raw material for mariculture activities. Those products are not accounted for a levelized cost estimative. Personally, I consider the comparison between OTEC and another ocean renewable as inadequate. A country with challenges involving water supply should adopt OTEC to produce desalinated water having energy as the byproduct, another country should be more involved with fish production and so on. This is a multipurpose  system with potential to provide many benefits.

OTEC Pilot Plants

There are several planned OTEC pilot plants around the world. This perspective is reinforced by the emergence of Ocean Thermal Energy Association (OTEA), a non-profit institution dedicated to promote OTEC and related ocean thermal technologies. The main challenge of OTEC supporters in their respective countries – that is may case in Brazil – is the persuasion of companies and investors about the advantages of investing in this type of technology and then rise funds to create a pilot plant.

Unlike wind turbines, which have reached technological maturity, OTEC systems still need to be tested in a higher scale for offshore environment in order to prove its feasibility. One of the main drawbacks to reach this goal is the lack of floating facilities, that comprise a big share of the capital expenditure. However, the recent decision for decommissioning of fixed and floating units in Brazilin oil and gas market represents a great opportunity.

An offshore pilot plant in a country with the characteristics detailed throughout this text is the natural step after many important achievements in other countries.   The success of Makai Ocean Engineering facilities (Figure 1), providing energy for 120 homes in Hawaii with an onshore OTEC pilot plant is an evidence of the need to move towards offshore. Makai Ocean engineering plans to build a 10 MW floating unit to provide clean energy to 120.000 homes (Figure 2).

Figure 1 – A 100 kW pilot plant built by Makai Ocean Engineering, supply energy for 120 homes.

Figure 2 – Onshore and offshore OTEC concepts (Makai Ocean Engineering).

The other successful pilot plant was built in Okinawa prefecture, Japan, supplying 100 kW for continuous supply of the city. This power was initially designed in order to test grid connection and supply stability. There are plans to increase the power supply in the future. (See more details in OTEC News).

Figure 3 – Okinawa pilot plant.

The Hawaii and Okinawa pilot plants prove the technical feasibility of OTEC. Nevertheless, the scale-up can bring new challenges especially related to performance, cost and environment. Besides those pilot plants others were already deactivated and there are others planned for the next years. There are great prospects in Indonesia, India and Malaysia, which keeps a partnership with Japan Government in the huge research program called SATREPS.

Environmental Conditions

Brazil is located in the tropical zone, where the surface sea water is warmer, an appropriate condition for OTEC, as well as other countries like Malasya, Indonesia, Australia, several African countries, India, Colombia, Mexico and Central America. Developed countries like Japan, England, Netherlands, United States and France can provide support for the development of OTEC with those tropical countries. In some cases this support already exists.

Figure 4 – Sea surface temperature in Brazilian coast during the winter. (IBGE, Atlas Geográfico da Zona Costeira Brasileira).

The dissertation prepared by Josiane Gomes Paulo, released by Federal University of Pernambuco in 2016, presents the thermocline along the notheastern brazilian coast. The data presented by Joseane Gomes Paulo indicates that the temperature of 5oC was reached at 600 m water depth in 2010 in the latitude of Pernambuco. This water depth changed to 400 m in 2012. This is an excellent scenario since a reduced Cold Water Pipe (CWP) increases the energy, reduces the cost and the risk of failure.  Temperature profile was also obtained from Argo Oceanography software, available in https://argo.ucsd.edu/. The temperature profile corresponds to the coast of Pernambuco in 2018.

Figure 5a – Thermocline in the coast of Pernambuco in 2010 and 2012, in different locations of the coast. (Dissertation of Josiane Gomes Paulo, 2016, UFPE).

Figure 5b – Thermocline in Pernambuco in 2018. (https://argo.ucsd.edu/).

Moreover, the Brazilian Economic Exclusive Zone is comprised by a 3.574.811 km2 area, of which one third is appropriated for OTEC. This huge area is suitable to provide not only energy but also fisheries, minerals – like diamond and gold – as well as oil and gas. For this reason this area was name by Brazilian Navy as Blue Amazon.  OTEC system is suitable for stimulating Blue Amazon activities as a support unit. This is in accordance with Avery & Wu (1994) which declare grazing units as the best option for OTEC, since it can adapt for the biggest temperature gradient. In the present case, an OTEC unit should be relocated according to a specific demand for refrigeration, fisheries, minerals, water or energy. This scenario makes OTEC a strategic asset.

Figure 6 – Blue Amazon , Exclusive Economic Zone (Brazilian Navy).

Oportunidades de Produ??o

As was previously informed a drawback of OTEC is its extremely low efficiency, which is achieved by high flow rates of sea water and working fluid. Despite this challenging condition the system can provide 24 h base energy, without the intermittency of wind and solar energy plants, although this intermittency can be compensated by batteries and other layouts.  The comparison between OTEC and other offshore energy techniques is premature since there is not an offshore power plant to provide reliable information for a levelized cost calculation. Everything is a bit theoretical when it comes to offshore OTEC.

The comparison based on power production does not apply to OTEC since there are potential byproducts that can increase the profits. This fact makes levelized cost comparison adequate if the OTEC platform is designed to produce only energy. Personally, I see energy as a byproduct if the main purpose of the plant is fisheries and water production, for example. When the French scientist George Claude came to Rio de Janeiro in 1920’s to test his floating OTEC facility his main objective was to sell ice to cariocas in the summer time. It is important to remind that refrigeration is another byproduct that can be useful in offshore oil and gas sector. It seems that OTEC can be useful in many ways, what makes it a unique ocean engineering solution – and that is why there are so many passionate about it.

The cold water pipe brings water from deep sea carrying nutrients which can be useful for mariculture activities. Brazil flaunts an enormous potential for fishing, mollusks, oyster and shrimp production, although it is still limited by a lack of an internal market to support industry development. Professor Ronaldo Cavali, from Federal University of Rio Grande do Sul, carried out a study regarding the brazilian offshore mariculture prospects (Cavali et al, 2011).  The author’s conclusion is that offshore activities will be possible after investments from private and government sectors and the attainment of research, especially related to Beijupirá (Figure 7), a commonly found species in Brazilian coast. 

Moreover, offshore mariculture reduces the social crisis due to competition among industry and artisanal fishing, as was explained by Hugo Juli?o Hermógenes in his PhD thesis, released in 2020 by Federal University of Paraná (Hermógenes, 2020).  Consequently an OTEC system can be part of a solution for a social conflict which grieves the fishing communities for decades, besides including Brazil among the providers of protein which will be demanded for the next decades according to the forecasts from FAO. 

Figure 7 – The increase of fishing production should be concentrated in the Beijupirá species.

Brazil is the thirteenth major aquiculture producer in the world (Figure 8), for this reason, ocean technologies with potential to increase fish production is not only an opportunity but a necessity for brazilian economy. Offshore mariculture has logistics and maintenance as the major difficulties for implementation, reducing competitiveness. An OTEC facility should be used as a monitoring station for mariculture operations while logistics should be shared with other renewable or offshore facilities.

Figure 8 – Brazilian fish production. (ABCC, 2018).

This layout is quite different from the current practice in offshore industry, however, the future synergy forecasted by IEA in the Offshore Energy Outlook (2018) will allow the sharing of logistic infrastructure among mariculture, oil & gas and renewable energy, that results in sharing the costs. Fishing production is not the only benefit of OTEC system since desalinated water is another byproduct. There are three main OTEC cycles, the first one is the closed one, characterized by a Rankine cycle. The second type is known as open cycle, characterized by a turbine driven by low pressure steam, that results in desalinated water after condensation (Figure 9).  The third type is the hybrid, which combines the characteristics of closed and open cycles.    

Figure 9 – Schematic diagram of Open Cycle for water production (Hamedi & Sadeghzadeh, 2017).

Unlike the fishing market, practically nonexistent in Brazil compared to its production potential the water demand is relevant for both industry and agriculture. The graph illustrated in Figure 10 indicates an increase of water demand in last years. Furthermore, it is important to remark that northeast region presents the second higher industrial water demand (Figure 11).  The building of the first Brazilian desalination plant will start this year in Ceará state, aiming to provide water for industrial sector. In addition to industry, Brazil can also start producing water for semi-arid region, also located in the northeastern region, which is characterized by one of the best land for agriculture, even though the lack of water.

Figure 10 – Increase of water demand for industry (National Water Agency, 2020).

Figure 11 – Water demand for each Brazilian region. Northeast in the second place. (ANA,2020).

Hydrogen and Zero Flaring

Oil & gas companies look for solutions to stop the waste of natural gas burned in the flares. An alternative is to export this gas instead of burn it. Some countries like Norway and Denmark lead the research and development for solutions that can mitigate or even eliminate the flaring and hydrogen is part of this solution.  According with Der Veer et al (2018) there are three hydrogen types classified in accordance with its production method. The first one is known as grey hydrogen, which is the result of the transformation of natural gas using the SRM method, currently used in 80% of operating plants. This method contributed to the emission of 1.25 million ton of CO2. The second type is the blue hydrogen, which is characterized by the sequestration of the CO2 produced by SRM. The expansion of offshore electrification will give rise to the green hydrogen, based in electrolysis. Jepma & Schot (2017) carried out a detailed study about green hydrogen, including cost analysis.

A pilot plant in Brazil should follow the route of blue hydrogen applying SRM to released gas followed by the Capture and Sequestration (CCS) of the CO2 produced. This method is technically mature and will likely stay as the most prominent technique in the next years, as was indicated by the report The Future of Hydrogen (IEA, 2019). Recently the CCUS (Carbon Capture Utilisation Storage) process has gained prominence, and is an alternative for the Brazilian pilot plant. In the work performed by Jepma & Schot (2017) they indicate that the energy transport to the coast using hydrogen should be limited by the lack of adequate facilities. It is also important to highlight the energy demand to liquefy the hydrogen, with an impact on the space necessary for hydrogen storage. One solution is to associate hydrogen to nitrogen, resulting in Ammonia, and excellent energy transport medium. Moreover, Ammonia is widely used in agriculture 

 Brown Fields and Oil & Gas Value Chain

As the oil and gas fields become older its recovery factor is progressively reduced. Some companies use specific injection techniques to increase this recovery factor. As OTEC is adequate for greezing and can be positioned in different regions along its life, there is an opportunity for energy supply to increase the recovery factor of those brown fields. This method would be in line with the National Petroleum Agency (ANP) strategy to increase the Brazilian oil and gas reservoir life (FGV, 2021). It is important to note that once again northeast region has an advantage, since most of the depleted reservoirs are in this place. 

According to IEA (2018) there is considerable potential for the utilization of the oil & gas sector activities to the offshore electrification. This superposition of activities is called synergy, allowing the sharing of resources for both industries. Besides electrification, offshore mariculture should also use the same value chain. For example, supply boats normally used for oil and gas production facilities should be also provide services for electrification and mariculture units. The same should happen with maintenance, pipelines, cables and transport. Shipyards should also be adjusted for building those renewable and mariculture facilities. This synergy favors the rise of a new industry, with positive impacts on the economical results. This can happen if Brazil install an OTEC pilot plant to evaluate not only the performance of the cycle but also the logistics and how the costs should be reduced with this synergy.

 Decomissioning

As oil and gas reservoir get older the infrastructure needs to be changed or removed following environment requirements. This activity is called decomissioning and there are prospects of an increase abandoned reservoir in the next years in Brazil. As discussed by International Energy Agency in the Offshore Energy Outlook (2018), there are different possibilities for using the disabled floating facilities. A possible use is the re-purpose, which includes offshore electrification. It means that there is a great opportunity to use Brazilian deactivated oil and gas platforms for OTEC pilot plants, not only in Brazil.

Figure 12 – Water demand for each Brazilian region. Northeast in the second place. (ANA,2020).

References

International Energy Agency, 2018, Offshore Energy Outlook

Landini, S., 2015, Competitiveness of Ocean Thermal Energy Conversion (OTEC) systems compared with other renewable technologies

Paulo, J.G., Distribui??o vertical dos nutrientes dissolvidos no nordeste do Brasil entre as latitudes 6o20s e 7o33s, UFPR, Departamento de Oceanografia, 2016

Avery W. , Wu C. , Renewable Energy from the Ocean, Oxford University Press, 1994

Cavali, R. Domingues, E.C., Hamilton, S., Desenvolvimento da Produ??o de Peixes em Mar Aberto no Brasil, Revista Brasileira de Zootecnia, v. 40, pp. 155-164, 2011

Hermógenes, H. J., O desenvolvimento recente da maricultura no Brasil: políticas de incentivo ao setor, impactos e injusti?as socioambientais nas comunidades pesqueiras artesanais, Tese, Departamento de Oceanografia, UFPR, 2020.

Revista da Associa??o Brasileira de Criadores de Camar?o, Ano XX, no. 2, Novembro de 2018, p. 8

Hamedi, A.S., Sadeghzadeh, S. , Conceptual design of a 5 MW OTEC power plant in the Oman Sea, Journal of Marine Engineering and Technology, 2017

Agência Nacional de águas, água na Indústria: Uso e coeficientes técnicos, 2017

Der Veer, E., Koornneef, J., Peters, R. , Offshore System Integration as a Transition Accelerator in the North Sea, 2018

International energy Agency, The Future of Energy, 2019

Jepma, C. J., Schot, M, On the economics of offshore energy conversion: smart combinations, Energy Delta Institute, 2017

Funda??o Getúlio Vargas, Caderno de Descomissionamento, FGV Energia, 2021