CleanTech is technology that reduces the consumption of resources (like energy) and the emission of toxins (like CO2e).
Smart CleanTech is CleanTech primarily based on information and communications technology (ICT).
CleanTech needs Smart CleanTech to succeed; Smart CleanTech needs Green ICT to stay clean itself.

SMART 2020: Enabling the low carbon economy in the information age helps us understand the potential value of Smart CleanTech:

...the biggest role ICTs could play is in helping to improve energy efficiency in power transmission and distribution (T&D), in buildings and factories that demand power and in the use of transportation to deliver goods.

In total, ICTs could deliver approximately 7.8 GtCO2e of emissions savings in 2020. This represents 15% of emissions in 2020 based on a BAU estimation. It represents a significant proportion of the reductions below 1990 levels that scientists and economists recommend by 2020 to avoid dangerous climate change. In economic terms, the ICT-enabled energy efficiency translates into approximately $946.5 billion of cost savings.

Our analysis identifies some of the biggest and most accessible opportunities for ICT to achieve these savings.
• Smart motor systems: Applied globally, optimised motors and industrial automation would reduce 0.97 GtCO2e in 2020, worth billion $107.2 billion.
• Smart logistics: The global emissions savings from smart logistics in 2020 would reach 1.52 GtCO2e, with energy savings worth $441.7 billion.
• Smart buildings: Globally, smart buildings technologies would enable 1.68 GtCO2e of emissions savings, worth $340.8 billion.
• Smart grids: Smart grid technologies were the largest opportunity found in the study and could globally reduce 2.03 GtCO2e, $124.6 billion. [1]

While the sector plans to significantly step up the energy efficiency of its products and services [Green ICT], ICT’s largest influence will be by enabling energy efficiencies in other sectors, an opportunity that could deliver carbon savings five times larger than the total emissions from the entire ICT sector in 2020.

Click on the "smart" tag at the top of this post for more about Smart CleanTech.

Estimate does not include benefits of smart grids beyond reduction of T&D [transmission and distribution] losses such as:
• DSM [Demand Side Management]
• Integration of renewables
• Improved asset management