HEMS Housing Comes into Focus: A Key Part of Home Generation and Storage

ORIGINAL: NikkeiBP

Apr 1, 2010 00:06 Mayuko Uno, Phil Keys

The Home Energy Management System (HEMS) is emerging as the next step in energy-saving home appliances. While HEMS can currently only display energy consumption data visually, even that has a significant effect. In the future when energy is generated and stored in the home, HEMS will be essential.

Reducing energy consumption in the home starts with reducing the electricity consumed by individual home appliances: improving the efficiency of constituent components and utilizing sensors to optimize operation.The next step will be to optimize the entire home.

HEMS manages energy throughout the home,networking energy-consuming equipment including home appliances and controlling them to reduce consumption. For the consumer, the advantage is lower utility bills with no loss in comfort.

Ten Percent Lower Just by Tracking Consumption

HEMS has two major functions,namely monitoring energy consumption,and controlling it to match the energy supply situation. At present it is utilized almost entirely for the former function,tracking energy consumption and presenting it visually to consumers.Just by making the data visually understandable, though, it helps users avoid energy wastage and is said to have considerable effect in cutting consumption. The Energy Conservation Center, Japan (ECCJ) has released the results of a survey indicating that merely making energy consumption data visible in one-hour units can cut consumption by about 10% annually.

The latter function, controlling consumption, is implemented to varying degrees.One commercial system available now will turn target systems on/off or alert the consumer when energy consumption over unit time exceeds a preset threshold.

Achieving CO₂-Neutral Homes within a Few Years

Energy generation and storage in the home will be combined with HEMS management of the energy supply/demand balance,reducing energy consumption together with energy-efficient appliances. Panasonic Corp. of Japan believes that this could reduce net CO₂ emissions from the home to zero,and has constructed an "Eco Idea House"as a concept model for the homes of a few years from now (Fig.1).

Fig 1. Reducing Home CO2 Emissions to Zero Panasonic hopes to makes it possible by combining home energy-conservation systems, fuel cells, solar power generation and storage batteries. The model is based on a 3-generation, 4-person family (grandfather, parents, daughter), in a 2-floor home with a floor area of 136.9m2.

According to a source at Panasonic,CO2 emissions from the home in 2009 have dropped to 47% of the 1990 level. The firm suggests that while the number of appliances in the home will increase from 78 (1990) to 97 in 201X, CO2 emissions will drop by another 12% to only 35% of 1990 levels.Even better,this 35% can be cut to net zero by using home fuel cells,solar power generating systems and storage batteries.

LEDs,Sensing and DC Supply

Of the reductions in consumption to be achieved over the next few years, 7% of the 1990 level will come from energy-efficient home appliances. For example, lighting will be from multiple indirect sources,combining distributed illumination with LEDs. Illumination sensors will be built into the home to automatically utilize multiple light sources depending on ambient light.This will eliminate unnecessary illumination,along with the power it wastes (Fig.2). Other factors contributing to lower energy consumption are the switch to plasma display panel (PDP) TVs,and lower stand-by power consumption by many types of appliances.

Fig 2. Illumination Adjusted for Ambient Light to Reduce Energy Consumption Light sensors detect ambient natural light and automatically adjust lighting,maintaining the optimal light level while reducing consumption by eliminating waste.

The other 5% will come from reduced energy consumption in electrical systems throughout the home, such as running direct current (DC) power in places. Electricity from DC sources such as solar power generation systems and fuel cells is currently converted to alternating current (AC) by power conditioners, with concomitant losses. Many appliances,however, are equipped with AC-DC converters to switch power back to DC,again causing loss. If power in the home were available from a DC supply, and could be provided to appliances with only voltage conversion, losses would be significantly reduced.

Panasonic expects that LED lighting,ventilator fans and other equipment will be supplied with DC power, directly driving the LED devices,motors and other key components. If DC wiring is installed in the home at construction, there would be no need for the user to worry about DC supply.

Panasonic suggests that the receptacles would still supply AC power, though,because very few home DC-supply home appliances are available for sale to consumers. During the transition period,probably a few years, AC and DC products would be mixed in the home, presenting safety

FIT System the Key to Storage Battery Adoption

For the remaining 35% of 1990 CO2 emissions, the combined use of city gas fuel cells,solar power generation and storage batteries to optimize electricity consumption in the home is expected to achieve CO2-neutral performance (Fig.3).

Fig 3. Three Power Supplies in the Home. The solar power generating system (5kW output) and fuel cells (1kW output) are commercially available (a,b).The fuel cells use city gas,with excess heat used to heat 200L to 60°C.The Li-ion rechargeable batteries (5kWh capacity) used for storage are prototypes,and commercialization has not been announced (c).

The only home power supply not available commercially at present is the storage battery, and Panasonic plans to use large-capacity Li-ion rechargeable storage batteries. A module of six such batteries, with a per-cell average voltage of 25.2V, current capacity 58Ah and battery capacity 1.5kWh would provide a total battery capacity of about 5kWh.

Panasonic Electric Works Co.,Ltd. of Japan says there are two factors influencing the widespread adoption of storage batteries: the feed-in tarrif (FIT) system for purchasing electricity generated by solar cells, and the spread of electric vehicles (EV). The FIT system for solar power generation launched in Japan in November 2009,setting fixed purchase prices for excess electricity generated by the consumer, for a 10-year period after application.The purchase price at program start was 48 yen/kWh, which is about twice the cost of electricity sold to the general public.

The purchase price for new contracts is reviewed annually, however, and discussion is under way on a plan to drop the price by 6 yen/year. Even if the FIT system does result in widespread adoption of solar power generation systems,there wouldn't be any profit left for newcomers in 2014 and beyond. This fact is increasing demand for storage batteries,as industry predicts that more and more people will elect to store and later consume their excess power instead of selling to the electric utility cheaply.

The obstacle to widespread adoption of storage batteries is the high price. A solar power generating system runs 2 to 3 million yen, and Panasonic believes that if the price of Li-ion rechargeable batteries could be reduced to several hundred thousand yen, the market would bear it. This price reduction is expected to be accomplished thanks to EVs. As EVs penetrate the market, it is hoped that the price of Li-ion rechargeable batteries will drop low enough to bring them into the home. Panasonic expects the price to drop before 2020.

With Storage Batteries Comes HEMS

Energy management and control via HEMS will be essential in efficiently handling power generation,storage batteries and grid supply. Panasonic believes that all storage battery installations will also have HEMS.

Panasonic describes a system that manages the flow of all energy in the home,including AC and DC power, gas and even water, controlling it for optimal efficiency (Fig. 4). It would provide advice via the flat screen TV or PC on how to save energy,along with information such as energy supply/demand status, CO2 emissions and reduction targets.

(4a) Energy supply display,including electrical power, water, and city gas used in fuel cells, as well as hot water usage

(4b) CO2 emission display. Energy usage and supply is shown for the day,the month and the year, indicating how CO2 emissions have changed

(4c) Energy usage display,showing present electricity consumption and sensor measurements

Fig.4 HEMS-Controlled Energy Supply the Key Energy management will be essential to utilize four supplies: solar power generation,storage batteries, fuel cells and the grid. The HEMS monitor screen can be displayed on the flat screen TV in the living room, for example. Prototype images shown.

HEMS is still developing.Panasonic Electric Works released the Eco-Management System for new home construction in October 2007, positioning it as a part of its "Lifinity" home networking system.

Current sensors mounted on distribution board branch circuits have been miniaturized (Fig.5), making it possible to display energy consumption in the home on a per-circuit basis and better promote energy-saving action on the part of the consumer (Fig.6). At present most systems are purchased together with solar power generating systems. in case of PanaHome, Eco-Management systems has been installed in 70% of the homes equipped with solar power generating systems.

Fig 5. Components Smaller than Ever Panasonic Electric Works has miniaturized components needed for energy consumption measurement,including CT sensors and image processing circuits.A distribution box of the same size as presently used can hold everything needed for up to 16 circuits.

While the cumulative quantity sold to the genera public by the end of 2009 was relatively low, only 200 to 300 units,this was double the quantity of the prior year. Half a dozen major home manufacturers and other firms now install Eco-Management systems as standard equipment in eco-conscious housing, and the trend is expected to accelerate. According to Toshiaki Tanaka,General Manager, New Business Promotion Department, Information Equipment &Wiring Products Manufacturing Business Unit of Panasonic Electric Works, "We hope to install systems into 5% to 10% of the 400,000 to 500,000 new homes we build in 2010.”

Distribution boards began to offer multiple circuits in about 2000, with all-electric homes offering dedicated circuits for each power-hungry appliance. As a result it as become quite a bit simpler to track per-unit power consumption at the distribution board.

For homes with pre-2000 installations it gets a bit harder to monitor power consumption. Even if the power is sensed at the distribution board,there are fewer branch circuits, and equipment such as washing machines or air conditioners may not be on a dedicated circuit.

Fig 6. Per-Circuit Energy Consumption Measurement and Control Current is measured for each circuit at the distribution board,tracking consumed power.

There are limits to how much can be accomplished at the distribution board, however. Ideally, HEMS would manage all information on a per-unit basis, receiving data from equipment and sending control signals, but as yet the required infrastructure and protocols have not been developed. Eco-Management Systems support the control functions for home automation defined by Japan Electrical Manufacturers' Association, referred to as JEMA-A. The standard was prepared for controlling air conditioners,in-floor heating systems and the like, however, and so only supports power on/off and thermostat functions.

Hoping to spread its home network system into existing homes,Panasonic Electric Works is considering joining the home information and communication technology (ICT) platform demonstration program under development by Nippon Telegraph and Telephone Corp. of Japan. They hope to utilize it to improve HEMS functions and interoperability with products from other vendors.

Demand for HEMS in Environment-Conscious Housing;ISP for mass housing complexes Interested in the Market

The HEMS market is taking off abruptly, and one of the factors appears to be the housing slump. Housing manufacturers and condo developers are looking for products to draw the buyer's eye, and focusing on environmentally conscious items. Part of this means increasing demand for HEMS.

FAMILYNET-JAPAN CORP., an Internet service provider (ISP) for mass housing complexes, will offer an "energy visualization service" in April 2010. The company began development in about 2008, in response to requests from condominium developers. It is positioned as an add-on service utilizing the Internet connection to extent home automation functions.

Initial costs can be split between multiple households in mass housing, resulting in a relatively lighter load. In many cases, Internet service in a mass housing complex is cheaper than private homes, generally running 1000 to 2000 yen/month. The new service option will probably only raise this by a few hundred yen.

Each resident will be able to check electricity usage and charges, as well as CO₂ emissions, for his unit over the Internet. Electricity is measured using ammeters mounted on branch circuits in the distribution board. The network system and the data transmission and storage server were newly developed. The system also offers functions such as displaying energy consumption for shared areas, and a ranking for units in the complex. The firm is also considering added a service to provide energy conservation advice to residents in fiscal 2010.

Chinese Appliance Manufacturer Haier Takes Aim at the HEMS Market

Haier Electronics Group Co. Ltd. of China has proposed U-home, a network interconnecting appliances and sensors in the home (FigB-1). Utilizing networks both inside and outside the home,U-home provides home networking functions to interconnect digital appliances, security functions (crime and disaster), home automation functions such as remote, batch and programmed control of lights and air conditioning, and energy-conservation functions such as energy consumption management.

[Fig.B-1 Networking Home Appliances, Sensors and More] An outline of Haier’s U-home home network system. Such small-scale home networks interconnect home appliances including hot water heaters, refrigerators, air conditioning, curtain mechanisms and lighting to magnetic, infrared and other sensors, cameras and security systems. The system handles data from electricity and water meters, as well as information on discount sales.