Sneha Sachar spent half of his time in Delhi and now lives in California, where he is used to heat it. But now her hometown feels much hotter than when she grew up.

Ms Sachar said that even for a certain number of months, it was so uncomfortable to get to and from work.

For outdoor workers, temperatures rise even lower. "It really affects people's ability to continue to win livelihoods," Ms. Sakar said.

She said there are many low-tech ways to keep buildings cool, such as designing for airflow.

For outdoor workers, even a 20-minute break with high temperatures and humidity (such as in a well-designed cooling station) may make a difference.

But beyond that, as climate change temperatures continue to rise, active cooling will become increasingly important.

Morgan Stanley predicts that the annual growth rate of the cooling market will reach US$23.5 billion (£180 million) by 2030.

However, existing cooling equipment has serious disadvantages. One problem is the refrigerant - a fluid that transitions back and forth to the gas during the transfer of heat.

They often leak out of standard systems, which can impair efficiency and potential health.

The refrigerant commonly used for cooling today is hydrofluoro compounds (HFCs), a group of synthetic gases with high global warming potential. HFC is more effective than carbon dioxide.

Therefore, one option is to replace the refrigerant with a more climate-friendly version. However, candidates with lower global warming potential also have problems.

For example, propane is highly flammable. Ammonia is toxic. Carbon dioxide works at high pressure and requires special equipment.

But because of many ground directions downward HFC, it will still be important to replace refrigerant.

Ms Sachar said we still need refrigerants because for home cooling, “as we know, at least for the next decade or so, we know they will continue to be solutions.”

In the long run, some scientists are looking for cooling devices that do not require liquid refrigerants at all.

Lindsay Rasmussen, who manages and land use projects on energy nonprofit RMI, calls these "revolutionary technologies".

A revolutionary set of cooling technologies is solid state cooling. This uses solid material and some additional force to induce temperature changes. This additional force may be pressure, voltage, magnet or mechanical stress.

Ms Rasmussen said solid-state devices can go a step further than gradual improvements because “not only do they eliminate those super-contaminated refrigerants, but they can also provide improved efficiency for the system”.

RMI has identified 10 to 20 startups working on earlier versions of solid-state cooling devices.

One of these startups is Magnotherm, a German company that uses magnets. Some materials change the temperature when exposed to a magnetic field.

"With our technology, it's inherently safe because it's not toxic, it's a metal and we're under very low pressure," said Timur Sirman, CEO and co-founder of Magnotherm.

The idea of ​​magnetization cooling has been around for years, but commercialization is relatively new. To date, Magnotherm has built refrigerators of about 40 beverage coolers and about five refrigerators.

Mr Sirman reported that permanent magnets are the most expensive part of the technology. “But it never breaks, so we can always reuse this rather cost-intensive component.”

The company is looking for alternative sources of magnetic fields as well as optimized materials as they aim to significantly improve the cooling capacity of the equipment.

Mr Sirman believes that if you address the efficiency and health of refrigerants, such as leaks, Magnotherm products can compete at prices. “We are not targeting customers who only have initial costs.”

He admits that for now, the company's beverage coolers are very expensive. Their customers are often early adopters of new technologies.

Another technology developed is thermoelectric cooling.

This involves moving heat on both sides of the device. With the application of electrical energy, heat is transferred in the direction of current.

A well-known thermoelectric starter is voice, which is located in the United States and has an additional manufacturing plant in Thailand.

Millions of tone cooling equipment are now being used, including in data centers, supermarkets and other buildings.

Their cooling equipment is built in a similar way to computer chips and uses semiconductor materials to transfer heat.

"Our chips are really thin, really small, but they're really cold. They'll consume a small amount of electricity to create this cold, but they're fighting a hell," said Tony Atti, Phonic's CEO.

He said that to do his best, traditional refrigerators need to be run all the time.

But thermoelectric devices can be turned on easily. This helps reduce costs, energy use and space requirements.

"We like to present a cool demand where it needs to," Mr. Artie said.

Another advantage is that the thermoelectric cooling can operate quietly. "That's because the moving parts are zero," Ms. Rasmussen explained. "The heat occurs due to the reaction at the material level."

In contrast, a standard vapor compression system includes a pump, condenser and extender for refrigerant, all of which produce a lot of noise.

Different types of solid state cooling are elastic cooling. This can achieve temperature variations through mechanical stress to elastic materials, which can be cooled or heated as pressure is applied.

Researchers from four European countries are working with Smacool, an elastic air conditioner that uses metal tubes made of specific metal alloys.

Currently, the cooling capacity of elastic prototypes is much lower than that of commercial air conditioners. The maximum possible efficiency of Smacool is still lower than that of conventional air conditioners, although its purpose is to beat A/C's energy efficiency.

However, progress is continuing. A team led by Hong Kong researchers recently created an A/C alternative that gained 1,284W of cooling capacity, the first time that the elastic device exceeds 1,000W. One innovation is the use of graphene nanofluids instead of distilled water to transfer heat.

Overall, solid-state devices are generally less powerful than conventional vapor compressed air conditioners, Ms Rasmussen said. But she expects performance to improve over time.

She also expects an improvement in affordability. So far, solid state cooling has been deployed primarily in wealthy countries.

A key question, Ms Rasmussen said, is “Can these technologies be extended to those who need it the most and the biggest need for cooling to afford it?”