Dimos Poulikakos1

1, ETH Zurich, Zurich, , Switzerland

Thermal energy, its transport and conversion, are critical aspects of the quest to develop the new generation of efficient energy technologies. Yet, traditionally, thermal energy is often not treated with needed care toward maximization of its potential with respect to all: its capturing, utilization, storage and eventually, the level at which it is considered as waste. Here I discuss cases of innovative technologies targeting to alleviate such deficiencies, all involving water as the working or targeted liquid.

To begin with, the Information Technology (IT) industry must play a key role in the global effort to reduce carbon-dioxide emissions with Low-Power High-Performance Computin, as it consumes 2% of the world energy with a strongupward trend. With this as a driver, I will demonstrate, the employment of an emerging, water-cooled processor architecture, exhibiting a higher efficiency in terms of MFlops/W, for the solution of challenging scientific problems and to harness the heat that is inevitably generated as close as possible to the source with a very high temperature level. This allows, for example, the heat to be re-used for space heating or process heat. The goal is to demonstrate a high performance, low power consumption datacenter/computing operation approaching zero net emission. The same approach amf developed devices can be taken to use the captured heat from the water cooling of high concentration photovoltaics for energy deficient applications running in parallel, such as desalination. Note here that geographically rich regions in solar radiation, often suffer simultaneously from fresh water scarcity.

Next, the current global electricity production stands at 23000 TWh with about 3000 TWh generated within Europe and is increasing steadily. It is likely to grow nearly 69% from present levels by 2040. However, more than 80% of the global electricity generation, and 48% of European power generation is based on the steam cycle that uses fossil fuels and nuclear fission1-3. This results in power generation being the largest contributor to greenhouse gas emissions (GHGs). Enhancing the thermal efficiency of a broad range of water condenser devices requires means of achieving sustainable dropwise condensation on metallic surfaces through surface micro- nanoengineering. To this end, I will discuss a rationally driven, hierarchical micro- nanotexturing process of copper surfaces, guided by fundamental principles of wettability and coalescence, which achieves controlled droplet departure under vapor flow conditions, significantly enhancing phase change thermal transport, by nearly 700% increase in heat transfer coefficients compared to filmwise condensation.

1. OECD Factbook 2015-2016 Economic, Environmental and Social Statistics; Paris, 2016.
2. European Commission. Electricity production, consumption and market overview; 2017.
3. International Energy Outlook 2016; 2016.