guia do novo coronavirus
Imprimir Republish

Electrical Engineering

Smart Shower

Company from Minas Gerais develops a system for recovering heat from bath water

disseminationPlatform with carpet and aluminum spiral that heats the waterdissemination

It was when he was in the middle of taking a shower and washing his feet that were dirty with red earth that technologist José Geraldo de Magalhães had an idea, as he watched the hot water running down the plug-hole. He thought about what a waste this was and began to imagine a system for taking advantage of this heat to help heat the very same shower water. Since September, and seven years after that day, in his home town of Rio Vermelho, in the Jequitinhonha Valley, Minas Gerais, Magalhães has been monitoring the free distribution of 7,000 of the devices invented by him for needy people in the Metropolitan Region of Belo Horizonte in a program prepared and funded by Cemig, the Minas Gerais Energy Company. Called a heat recoverer for electric showers, the system makes it possible for a home to cut its spending on electricity by 44%. The recoverer is produced by Rewatt Ecológica, of which Magalhães is one of the partners.

It works in a very simple way. Instead of the water from the tank or public distribution network going straight to the shower it comes in through a hosepipe and arrives at a reinforced plastic platform installed in the floor of the shower. This platform is 58 cm in diameter and 4 cm high, with a carpet and anti-slip structure. Within this device there is an aluminum heat exchanger in the shape of a spiral tube that recovers the hot water from the shower and in about 20 seconds heats the clean water that is inside the pipe. The heated water goes up the shower head by natural pressure, or using a pressurizer.

The difference with the new system is that when the water reaches the shower head it is already pre-heated as compared to the water in the (cold) tank. Normally natural water starts at around 20º Celsius (C) and is heated in the shower to 38ºC, which is the temperature of a hot shower in winter. “If it’s already at 27ºC, the difference drops from 18º to 11ºC”, says Professor Júlia Maria Garcia Rocha, from the Studies and Energy Group (Green) of the Polytechnic Institute of the Pontifical Catholic University of Minas Gerais (PUC Minas). She coordinated the two tests that proved the technical feasibility of the system, first at the request of Magalhães and after of Cemig. “At first we didn’t believe that the recoverer would work. Later we carried out tests, the theoretical modeling and in the end made suggestions for improving the equipment”, says Júlia. “I was so impressed that I installed a recoverer in my home.”

The savings are more apparent when the shower is changed. “This device is the villain when it comes to energy spending in a home and with the heat recoverer it’s possible to have a less powerful shower”, says Magalhães. Therefore, instead of a 5,400 watt shower, for example, one can use a 3,200 watt shower that works well, even in winter, or an even less powerful one, depending on the region. “I sold one of the first prototypes for a field test in Carlos Barbosa, in Rio Grande do Sul, close to Caxias do Sul. There, they replaced a 7,400 watt shower by a 4,400 watt one”, says Magalhães.

Another successful case mentioned by Magalhães, but still in the experimental phase, was the installation of nine heat recoverers in a sports center in Pedro Leopoldo, in Minas Gerais, in the Metropolitan Region of Belo Horizonte. The 5,400 watt showers were replaced by 2,000 watt ones while the 4,400 watt showers replaced by 1,800 watt ones. After 30 days, the power savings amounted to 1,020 kWh according to the light bill, resulting in savings of R$ 612 in the center’s expenses.

The consumption of electricity in homes accounts for 24% of the total power used in Brazil, or 83,000 MWh a year, according to the Energy Research Company (EPE) of the Ministry of Mines and Energy. Of this figure, 26 – 32% represents the heating of water for showers, of which a large part is concentrated at peak times, between 6:00 pm and 9:00 pm. Therefore, national spending on power just for taking showers is around 22,000 MWh. According to Rewatt, if all Brazilian showers adopted the heat recoverer the savings would equal 2.56% of the country’s total power consumption, or about 8,000 MWh, similar to the annual energy needs of the State of Goiás, for example.

For the time being, Rewatt’s system will only be available on a large scale in those homes selected by Cemig’s Conviver Project, the objective of which is to implement energy efficiency actions and bring the company closer to those people who need it most. “Those who are going to be given the system live in homes with more than four people, are up to date in their payments and have an annual average consumption of at least 90 kWh per month”, says the Conviver Project coordinator, Henrique Fernando França Costa. In addition to the recoverer, the project will also distribute some 300,000 compact light bulbs free of charge to replace the incandescent bulbs that use more energy. This year, Cemig plans to invest R$ 21.5 million in the program. The recoverers represent an investment of R$ 2.4 million. The initiative is connected with a resolution issued by the National Electrical Energy Agency (Aneel), which has indicated that all electricity concessionaires must invest 1% of their net operating revenues in R&D and in energy efficiency projects. In the case of the Conviver Project, another important factor is the generation of additional income for the family, as it will be spending less on electricity. Communities also benefit, because the installers of the heat recoverers will be recruited locally. Training is being done by Rewatt and Cemig.

The success of Magalhães’ invention began right after the original idea in Rio Vermelho. “I had a company that installed and repaired air conditioning for automobiles and after registering the patent for the invention with the National Industrial Property Institute (INPI), I made around a hundred prototypes of the recoverer. In the end I was looking for the best shape, beauty and functionality”, recalls Magalhães, who is a building technology graduate from the Federal Center of Technological Education of Minas Gerais (Cefet-MG), in Belo Horizonte. “I looked for international patents and I found something similar in Germany and England, but the equipment wasn’t working there. I stubbornly insisted on the recoverer but ended up bankrupting my company.” That is when he decided to look for partners to manufacture the equipment. He was at an inventors’ fair in the Expominas Pavilion in March 2005, in Belo Horizonte, when consultant and company administrator Valério José Monteiro heard about the invention and became interested in making the product viable. “In April 2005, after countless conversations, we put together a good business plan and went looking for capital in the market. We had some investors who liked the idea but didn’t believe in the company’s potential. We persisted until we met Marco Antônio Almeida Resende, who came in as an investing partner, injecting R$ 200,000, plus two years of a lot of dedication and hard work. That’s how we managed to complete development of the recoverer”, says Monteiro. He says that the companies that supply parts also came into the project as risk partners. In 2006, Rewatt offered the product to Cemig, which right away hired the company as its partner in the energy efficiency project.

The second step for Rewatt will be to launch the product onto the market. “We’re structuring ourselves to sell the recoverer to a wider public as from January 2008. At a cost of approximately R$ 360, the product pays for itself in ten months when used in a house with up to four people. There are cases in which the savings may reach 50% of the electricity bill, thereby reducing the amortization period”, says Monteiro. “We’re going to focus on the distributor market in the South and Southeast initially.” In the meantime inventor Geraldo Magalhães, at 56, is still thinking of innovations and new inventions. He believes he can transpose this system to other ways of heating baths, like those that exist in heating chambers, called boilers, such as those used in other Latin American countries and in Europe, for example, where electric showers do not exist. “As far as I know, showers like we have in Brazil only exist in Peru. The heat recoverer can be adapted to the heating processes in any country. We just need a specific project”, says Magalhães. He prefers not to talk about other inventions. “I’m still studying them.”