The door had barely opened a crack when Chen Hao's voice squeezed in: "Hey! This box is stuck! Come and lend a hand!"

Nana immediately stood up from the control panel, her optical lens quickly scanning the hallway outside. The transport container lay across the corner, its bottom sealed by a thin layer of ice, its sides pressed against the walls, completely immobile. She hurried to the doorway and crouched down to examine the floor.

“Ice formation increases friction,” she said. “Dragging directly on it could damage the shock-absorbing structure.”

Chen Hao stood at the other end of the box, his hand resting on the metal casing, his breath condensing into white mist in the cold air. "So what do you suggest we do? We can't just wait for it to melt away, can we?"

“I have a way.” Nana turned and went back into the house, taking a discarded circuit board from the tool shelf. “Use this to scrape away the ice and create a slide.”

She crouched down and carefully scraped away the ice with the edge of a circuit board. Chen Hao, seeing this, also realized what was happening and ran to remove half of the metal base of the sled, laying it diagonally across the passage to form a makeshift guide rail.

"You're really quick-witted," he said as he straightened the box. "How about you let me win a game of chess next time?"

“The current task takes priority over entertainment.” Nana pushed the box, the metal base scraping against the ground with a hissing sound. “But if you can complete three effective operations, I will consider adjusting the strategy weights.”

"Alright, here we go again." Chen Hao grinned. "Anyway, I'm used to you not keeping your word."

The two of them worked together to push the box to the processing area and gently placed it down. Nana opened the sealing lock and lifted the lid. Inside were six optical lenses neatly arranged, their surfaces smooth as water, gleaming coldly under the light.

"It has a reflectivity of 92%," she said. "It can be used to focus sunlight and improve heat collection efficiency."

"Sounds pretty impressive." Chen Hao reached out to touch it. "Is this thing really not afraid of being dropped?"

"Don't touch it." Nana raised her hand to stop her. "It's fragile. Vibration exceeding three bars will cause micro-cracks."

"Okay, okay, I won't touch it." He withdrew his hand and patted his pants. "So what's next? Mount it on the wall?"

"First, assemble the support frame." Nana brought up the 3D model projection. "Use discarded circuit boards as the base, copper pipes as the heat conduction circuit, and carbon-coated glass as the heat absorption surface."

Chen Hao looked at the structural diagram on the projector and scratched his head. "Isn't this just like building Lego?"

“The analogy works,” Nana nodded. “The difference is that a misspelling will cause water to leak.”

"Then I'll have to be serious." He picked up the wrench and walked toward the pile of materials.

The two had a clear division of labor. Nana was responsible for calibrating the angle and connecting the control system, while Chen Hao built the main framework. He fixed four pieces of carbon-coated glass to the outside of the south wall and tightened the bases with screws. Copper pipes were welded to the back of each piece of glass to transfer heat.

“The next step is lens installation,” Nana said. “Precise focusing is essential; otherwise, excessively high local temperatures can cause the solder joints to melt.”

“Then you take charge, and I’ll manage.” Chen Hao wiped his sweat. “Although I’m clumsy, at least I can understand human speech.”

Nana activated the laser positioning assistance system, marking a 37-degree tilt angle on the lens holder. She gently lifted the first lens with the robotic arm and slowly adjusted its position. Chen Hao stood beside her, holding the support frame, afraid it would shake.

“A little more to the left…stop!” he said. “Look at that corner over there, the reflection is shining right in the middle of the glass.”

Nana recorded the parameters. "Angle correction complete, first piece in place."

There was a problem during the installation of the second lens. As soon as the lens was fixed in place, sunlight pierced through the clouds and instantly focused on the copper tube joint. The metal turned red, and the sealant started to smoke.

"Oh no!" Chen Hao grabbed a heat-insulating pad and slammed it on. "The solder joint is going to burn through!"

Nana immediately cut off the light path and turned off the lens deflection. "The local heat load is exceeding expectations, and the thermal design needs to be optimized."

Chen Hao, panting, looked at the blackened pipes. "This won't work. All the heat is trapped in one place; it'll explode sooner or later."

He pondered for a moment, then suddenly looked up: "Could we change the copper pipe to a serpentine shape? Wrap it around a few more times to distribute the heat?"

Nana quickly modeled and analyzed the data. "Feasible. The dual-loop layout can reduce the heat flux density per unit length."

“Let’s get started.” Chen Hao rolled up his sleeves. “I’ll weld the new one.”

He rearranged the copper pipes, bending them into a wavy shape, and connected both ends to the main circulation system. He worked slowly during welding, but carefully polished and sealed each joint. Nana monitored the airtightness to ensure there were no leaks.

"The structure is complete," she said. "Ready to connect to the heating pipes."

Chen Hao wiped the dust off his face. "We can try it once the sun comes out."

They returned to the control room and waited for noon. Outside the window, the clouds were thinning, and sunlight occasionally pierced through, drawing bright stripes on the snow.

"The optimal light intensity is expected to be reached at 12:07." Nana stared at the weather data. "I suggest starting the preheating program in advance."

"Warm-up?" Chen Hao asked. "Isn't it enough to just expose it to the sun directly?"

“Glass surfaces are prone to condensation,” she said, “which affects heat absorption efficiency.”

She activated the backup heating element, briefly powering on the heat collector outside the door. After a few minutes, the surface moisture evaporated, and the view became clear again.

“The control system interface is aging.” Nana continued debugging. “The signal delay is 0.8 seconds, and it needs to be manually calibrated.”

She tossed a few switches to resynchronize the communication frequency. The connection status on the screen changed from red to green.

"Okay," she said, "water can come in now."

Chen Hao rushed to the window and stared at the sunlight outside. A beam of strong light fell directly on the lens, reflecting off the center of the carbon-coated glass.

"Now!" He pressed the water inlet valve button.

Water flowed slowly into the copper pipe. On the monitor, the temperature curve began to rise slowly. One minute later, the water temperature rose from five degrees to nine degrees; three minutes later, it reached twelve degrees.

“The heat input is stable.” Nana read the data. “The current efficiency is 64% of the expected value.”

"Only 60%?" Chen Hao frowned. "That's far from enough."

"After 15 minutes of continuous illumination, the efficiency increased to 78%." She pulled up the chart, "which meets the initial operating standards."

Chen Hao stared at the screen and suddenly smiled. "Not bad, it's a success as long as it wasn't completely destroyed on the spot."

“The system has been running continuously for two hours,” Nana said. “There have been no leaks or structural deformations.”

“We worked well together.” He leaned back in his chair and stretched. “Looks like you’re not just good at math after all.”

“Your welding process still has room for improvement,” Nana said. “The third node is not sealed evenly, posing a potential risk of leakage.”

"Fine, you start finding fault as soon as you open your mouth." Chen Hao waved his hand. "Can't you at least let me say something nice?"

"Objective evaluation helps improve the quality of work."

"How many times have you said that?" He yawned. "Anyway, it's finally done today. The solar energy project is finally getting moving."

Nana pulled up an energy consumption comparison chart. "Fuel consumption rate decreased by 19%, and the remaining usage period has been extended to twenty-one days."

"Three weeks." Chen Hao squinted. "That's enough time for us to catch our breath."

He stood up and walked to the window to look at the solar collector outside. The black glass panel gleamed dimly in the sunlight, and the lenses were slightly adjusted, like a group of quietly watching eyes.

"Shouldn't we start thinking about geothermal energy next?" he asked.

“We currently lack drilling equipment,” Nana said. “It cannot be implemented in the short term.”

“I know,” Chen Hao said, leaning against the window frame. “But we have to have a plan, right? Solar energy depends on the weather. If it’s cloudy for ten or fifteen days, we’ll be out of a job.”

"Under the existing conditions, this is the most feasible solution."

“I’m not against it,” he said. “I’m saying we can’t rely on just one thing.”

Nana paused for two seconds. "We can start planning a feasible path and proceed once resources are replenished."

"That's more like it." Chen Hao nodded. "Once we find a drilling rig, we'll get to work right away."

He turned to leave, but his foot slipped and he almost tripped. Looking down, he saw a piece of sealant residue stuck to the sole of his shoe.

"How long has it been since this floor was mopped?" he muttered. "It looks like a construction site."

“Cleaning is not currently on the task list,” Nana said. “We recommend prioritizing system stability monitoring.”

"All you ever think about is missions, missions." Chen Hao walked to the control panel and sat down. "Fine, I'll keep an eye on things with you."

The data on the monitoring screen kept fluctuating. Thermal input remained stable, and efficiency stayed above 75%.

"At this rate, we can break 80% by tomorrow," Nana said.

"That's great." Chen Hao rubbed his eyes. "But I'm a little sleepy now. I stayed up late drawing last night."

“You can rest for thirty minutes,” Nana said. “I will monitor the operation.”

"You're so thoughtful." He chuckled, tilting his head back in his chair. "If you ever learn how to cook instant noodles, I'll consider you my older sister."

His breathing gradually became heavier. Nana did not respond, but simply raised the alert level to level two and continued recording the data changes every five minutes.

Three hours later, Chen Hao opened his eyes and sat up straight. "How is it? Did it explode?"

"The system is operating normally," Nana said. "The cumulative heat input has reached 82% of the expected daily target."

"Wow, that's pretty good." He rubbed his face and looked at the screen. "Better than I expected."

He stood up, walked to the control panel, and reached out to touch the data panel.

"Your fingers are too oily," Nana reminded. "Please clean them before proceeding."

"I didn't do it on purpose." Chen Hao withdrew his hand. "How can you not get tools dirty if you touch them all day?"

He wiped his hands with a wet wipe and moved closer to the screen. "What's next? Add a second set of lenses? Or get a more powerful pump?"

"I suggest conducting a comprehensive inspection first," Nana said. "Check all connection points for any micro-leakage."

"Okay, I'll do as you say." Chen Hao picked up the testing device. "Let's go, let's get to work."

He had just opened the door when a cold draft rushed in. Outside, the setting sun cast its last rays on the solar collector, reflecting a long, thin spot of light that fell directly onto the floor of the control room.

Chen Hao stepped out into the light and turned back to say, "This thing is pretty bright."

Nana followed behind him, and the robotic arm gently lifted to adjust the angle of the last lens.

The light spot moved an inch.