Next-generation green base station

Responding to the growing demand for energy-efficient telecommunications infrastructure and stronger disaster countermeasures following the Great East Japan Earthquake, NTT DOCOMO has started to deploy next-generation green base stations in line with its SMART for GREEN 2020 environmental vision. Green base stations are designed to consume less commercial electricity from power utilities by being fitted with devices such as solar panels, wind turbines, fuel cells and DC green power controllers. They are also equipped with lithium-ion rechargeable batteries that store surplus electricity that can be used during power consumption peaks or power outages caused by disasters.

NTT DOCOMO plans to deploy 10 next-generation green base stations by the spring of 2013, and is also constructing a system for visualizing power supply and demand in its base stations throughout Japan, and conducting R&D aimed at creating its own smart grid for sharing power among multiple green base stations.

Photo: Hokuto City

Under a project commissioned by the New Energy and Industrial Technology Development Organization (NEDO), NTT FACILITIES conducted research from fiscal 2007 to fiscal 2011 aimed at verifying grid stabilization of large-scale solar power generation systems.

The project involved the building of a large-scale system with a generation capacity of 1.84 MW in Hokuto City, Yamanashi Prefecture, a location blessed with more sunlight on average than anywhere else in Japan, to develop grid stabilization technologies for eliminating any adverse impacts on a grid of the fluctuating output inherent to solar power systems, and to ascertain the power generation capabilities of different types of photovoltaic cells.

In fiscal 2012, NTT FACILITIES completed a report presenting the findings of its five years of research, together with STEP-PV (Simulation Tools for Estimating system output Power of a largescale PV plant) by enabling estimation of power output and environmental contribution. These and earlier findings have been published on NEDO's website to contribute to the smooth deployment of solar power generation systems.

The Hokuto facility is currently being used by the city of Hokuto as an environmental education site that attracts approximately 5,000 visitors per year.

NTT COMWARE's fully fresh air-cooled data center

Exhaust fans for expelling heat generated by ICT equipment

Motorized damper (air intake side) for drawing in fresh air

Responding to growing demands to reduce data center costs and energy consumption, NTT COMWARE in November 2011 started testing an energy-efficient fresh air-cooled data center that delivers cost savings and has a smaller environmental footprint than conventional data centers.

The test data center takes in fresh air and expels air heated by the operation of ICT equipment, eliminating the need for cooling systems and reducing the environmental footprint by cutting air conditioning-related electricity consumption by 20% compared with previous NTT COMWARE data centers. The use also of DCdriven ICT equipment to minimize AC/DC power conversion losses and other measures enabled the achievement of a PUE^* of less than 1.1 during the six-week testing period.

NTT COMWARE is planning to carry out year-round testing with a view to the eventual use of such data centers for its SmartCloud enterprise cloud services.

Tenant liaison meeting

In addition to fitting buildings with energy-efficient equipment when constructing them, the everyday management of buildings once they are in use can also make a big difference to their energy efficiency. This is why the NTT Urban Development Group is taking measures to reduce energy consumption and CO2 emissions by improving the energy management of its buildings based on detailed status monitoring.

At the core of such efforts are building and energy management systems (BEMS) that enable more efficient energy use through managing the operation of a building's fittings and other equipment. The NTT Urban Development Group established an Energy Management Center (EMC) in 2005 to analyze BEMS measurements and formulate measures for system control optimization, and EMC has since provided both the Group and its tenants with suggestions for efficient energy use, as well as fine-tuning BEMS to best match building load.

EMC has developed a methodology based on the results of its analysis, and has since 2008 regularly published papers on its findings in the Journal of the Society of Heating, Air-Conditioning and Sanitary Engineers of Japan. The measures developed as a result of these efforts are also being applied to other buildings to help save energy, and reduce CO2 emissions and energy costs. The NTT Urban Development Group, which owns over 100 buildings nationwide, has so far deployed BEMS in 12 large-scale properties.

Also, it is becoming increasingly important for building owners to enlist the cooperation of tenants to supplement their own efforts to achieve further energy savings and CO2 emission reductions. The NTT Urban Development Group in fiscal 2011 accordingly started to hold tenant liaison meetings for large-scale properties coming under Tokyo Metropolitan Government's Environment Protection Ordinance.